1. Physical Quantities, Units and Measurement



Syllacon NOTESSINGAPORE-CAMBRIDGE GCE O-LEVELPHYSICS OUTLINESYLLABUS 5059UPDATED 20 JAN 2014OverviewThemesChaptersCountI. Measurement11II. Newtonian Mechanics2-76III. Thermal Physics8-114IV. Waves12-154V. Electricity & Magnetism16-227 TOC \o "1-1" \h \z \u 1. Physical Quantities, Units and Measurement PAGEREF _Toc377943334 \h 122. Kinematics PAGEREF _Toc377943335 \h 173. Dynamics PAGEREF _Toc377943336 \h 204. Mass, Weight and Density PAGEREF _Toc377943337 \h 235. Turning Effect of Forces PAGEREF _Toc377943338 \h 256. Pressure PAGEREF _Toc377943339 \h 277. Energy, Work and Power PAGEREF _Toc377943340 \h 298. Kinetic Model of Matter PAGEREF _Toc377943341 \h 329. Transfer of Thermal Energy PAGEREF _Toc377943342 \h 3410. Temperature PAGEREF _Toc377943343 \h 3611. Thermal Properties of Matter PAGEREF _Toc377943344 \h 3712. General Wave Properties PAGEREF _Toc377943345 \h 4113. Light PAGEREF _Toc377943346 \h 4414. Electromagnetic Spectrum PAGEREF _Toc377943347 \h 4915. Sound PAGEREF _Toc377943348 \h 5116. Static Electricity PAGEREF _Toc377943349 \h 5417. Current of Electricity PAGEREF _Toc377943350 \h 5818. D.C. Circuits PAGEREF _Toc377943351 \h 6319. Practical Electricity PAGEREF _Toc377943352 \h 6520. Magnetism PAGEREF _Toc377943353 \h 6921. Electromagnetism PAGEREF _Toc377943354 \h 7122. Electromagnetic Induction PAGEREF _Toc377943355 \h 77Note to student:Spot an error? Think that you can improve the outline?Download the .docx format of this document from the website and edit the outline yourself!Alternatively, you may wish to email the site owner at lim.ting.jie.2012@vjc.sg with the subject title: ‘Outline Feedback: O Level Physics Outline’Contents TOC \o "1-3" \h \z \u 1. Physical Quantities, Units and Measurement PAGEREF _Toc378015365 \h 12(a) show understanding that all physical quantities consist of a numerical magnitude and a unit PAGEREF _Toc378015366 \h 12(b) recall the following base quantities and their units: mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol) PAGEREF _Toc378015367 \h 12(c) use the following prefixes and their symbols to indicate decimal sub-multiples and multiples of the SI units: nano (n), micro (μ), milli (m), centi (c), deci (d), kilo (k), mega (M), giga (G) PAGEREF _Toc378015368 \h 12(d) show an understanding of the orders of magnitude of the sizes of common objects ranging from a typical atom to the Earth PAGEREF _Toc378015369 \h 12(e) state what is meant by scalar and vector quantities and give common examples of each PAGEREF _Toc378015370 \h 13(f) add two vectors to determine a resultant by a graphical method PAGEREF _Toc378015371 \h 13(g) describe how to measure a variety of lengths with appropriate accuracy by means of tapes, rules, micrometers and calipers, using a vernier scale as necessary PAGEREF _Toc378015372 \h 14(h) describe how to measure a short interval of time including the period of a simple pendulum with appropriate accuracy using stopwatches or appropriate instruments PAGEREF _Toc378015373 \h 152. Kinematics PAGEREF _Toc378015374 \h 17(a) state what is meant by speed and velocity PAGEREF _Toc378015375 \h 17(b) calculate average speed using distance travelled / time taken PAGEREF _Toc378015376 \h 17(c) state what is meant by uniform acceleration and calculate the value of an acceleration using change in velocity / time taken PAGEREF _Toc378015377 \h 17(d) interpret given examples of non-uniform acceleration PAGEREF _Toc378015378 \h 18(e) plot and interpret a displacement-time graph and a velocity-time graph PAGEREF _Toc378015379 \h 18(f) deduce from the shape of a displacement-time graph when a body is: (i) at rest (ii) moving with uniform velocity (iii) moving with non-uniform velocity PAGEREF _Toc378015380 \h 18(g) deduce from the shape of a velocity-time graph when a body is: (i) at rest (ii) moving with uniform velocity (iii) moving with uniform acceleration (iv) moving with non-uniform acceleration PAGEREF _Toc378015381 \h 18(h) calculate the area under a velocity-time graph to determine the displacement travelled for motion with uniform velocity or uniform acceleration PAGEREF _Toc378015382 \h 19(i) state that the acceleration of free fall for a body near to the Earth is constant and is approximately 10 m/s2 PAGEREF _Toc378015383 \h 19(j) describe the motion of bodies with constant weight falling with or without air resistance, including reference to terminal velocity PAGEREF _Toc378015384 \h 193. Dynamics PAGEREF _Toc378015385 \h 20(a) apply Newton's Laws to: (i) describe the effect of balanced and unbalanced forces on a body (ii) describe the ways in which a force may change the motion of a body (iii) identify action-reaction pairs acting on two interacting bodies (stating of Newton's Laws is not required) PAGEREF _Toc378015386 \h 20(b) identify forces acting on an object and draw free body diagram(s) representing the forces acting on the object (for cases involving forces acting in at most 2 dimensions) PAGEREF _Toc378015387 \h 21(c) solve problems for a static point mass under the action of 3 forces for 2-dimensional cases (a graphical method would suffice) PAGEREF _Toc378015388 \h 21(d) recall and apply the relationship resultant force = mass × acceleration to new situations or to solve related problems PAGEREF _Toc378015389 \h 22(e) explain the effects of friction on the motion of a body PAGEREF _Toc378015390 \h 224. Mass, Weight and Density PAGEREF _Toc378015391 \h 23(a) state that mass is a measure of the amount of substance in a body (b) state that mass of a body resists a change in the state of rest or motion of the body (inertia) PAGEREF _Toc378015392 \h 23(c) state that a gravitational field is a region in which a mass experiences a force due to gravitational attraction PAGEREF _Toc378015393 \h 23(d) define gravitational field strength, g, as gravitational force per unit mass PAGEREF _Toc378015394 \h 23(e) recall and apply the relationship weight = mass × gravitational field strength to new situations or to solve related problems PAGEREF _Toc378015395 \h 23(f) distinguish between mass and weight PAGEREF _Toc378015396 \h 24(g) recall and apply the relationship density = mass / volume to new situations or to solve related problems PAGEREF _Toc378015397 \h 245. Turning Effect of Forces PAGEREF _Toc378015398 \h 25(a) describe the moment of a force in terms of its turning effect and relate this to everyday examples (b) recall and apply the relationship moment of a force (or torque) = force × perpendicular distance from the pivot to new situations or to solve related problems PAGEREF _Toc378015399 \h 25(c) state the principle of moments for a body in equilibrium (d) apply the principle of moments to new situations or to solve related problems PAGEREF _Toc378015400 \h 25(e) show understanding that the weight of a body may be taken as acting at a single point known as its centre of gravity PAGEREF _Toc378015401 \h 25(f) describe qualitatively the effect of the position of the centre of gravity on the stability of objects PAGEREF _Toc378015402 \h 266. Pressure PAGEREF _Toc378015403 \h 27(a) define the term pressure in terms of force and area (b) recall and apply the relationship pressure = force / area to new situations or to solve related problems PAGEREF _Toc378015404 \h 27(c) describe and explain the transmission of pressure in hydraulic systems with particular reference to the hydraulic press PAGEREF _Toc378015405 \h 27(d) recall and apply the relationship pressure due to a liquid column = height of column × density of the liquid × gravitational field strength to new situations or to solve related problems PAGEREF _Toc378015406 \h 28(e) describe how the height of a liquid column may be used to measure the atmospheric pressure PAGEREF _Toc378015407 \h 28(f) describe the use of a manometer in the measurement of pressure difference PAGEREF _Toc378015408 \h 287. Energy, Work and Power PAGEREF _Toc378015409 \h 29(a) show understanding that kinetic energy, potential energy (chemical, gravitational, elastic), light energy, thermal energy, electrical energy and nuclear energy are examples of different forms of energy PAGEREF _Toc378015410 \h 29(b) state the principle of the conservation of energy and apply the principle to new situations or to solve related problems PAGEREF _Toc378015411 \h 29(c) calculate the efficiency of an energy conversion using the formula efficiency = energy converted to useful output / total energy input PAGEREF _Toc378015412 \h 29(d) state that kinetic energy Ek = ? mv2 and gravitational potential energy Ep = mgh (for potential energy changes near the Earth’s surface) (e) apply the relationships for kinetic energy and potential energy to new situations or to solve related problems PAGEREF _Toc378015413 \h 30(f) recall and apply the relationship work done = force × distance moved in the direction of the force to new situations or to solve related problems PAGEREF _Toc378015414 \h 30(g) recall and apply the relationship power = work done / time taken to new situations or to solve related problems PAGEREF _Toc378015415 \h 308. Kinetic Model of Matter PAGEREF _Toc378015416 \h 32(a) compare the properties of solids, liquids and gases PAGEREF _Toc378015417 \h 32(b) describe qualitatively the molecular structure of solids, liquids and gases, relating their properties to the forces and distances between molecules and to the motion of the molecules PAGEREF _Toc378015418 \h 32(c) infer from Brownian motion experiment the evidence for the movement of molecules PAGEREF _Toc378015419 \h 32(d) describe the relationship between the motion of molecules and temperature PAGEREF _Toc378015420 \h 33(e) explain the pressure of a gas in terms of the motion of its molecules PAGEREF _Toc378015421 \h 33(f) recall and explain the following relationships using the kinetic model (stating of the corresponding gas laws is not required): (i) a change in pressure of a fixed mass of gas at constant volume is caused by a change in temperature of the gas (ii) a change in volume occupied by a fixed mass of gas at constant pressure is caused by a change in temperature of the gas (iii) a change in pressure of a fixed mass of gas at constant temperature is caused by a change in volume of the gas PAGEREF _Toc378015422 \h 33(g) use the relationships in (f) in related situations and to solve problems (a qualitative treatment would suffice) PAGEREF _Toc378015423 \h 339. Transfer of Thermal Energy PAGEREF _Toc378015424 \h 34(a) show understanding that thermal energy is transferred from a region of higher temperature to a region of lower temperature PAGEREF _Toc378015425 \h 34(b) describe, in molecular terms, how energy transfer occurs in solids PAGEREF _Toc378015426 \h 34(c) describe, in terms of density changes, convection in fluids PAGEREF _Toc378015427 \h 34(d) explain that energy transfer of a body by radiation does not require a material medium and the rate of energy transfer is affected by: (i) colour and texture of the surface (ii) surface temperature (iii) surface area PAGEREF _Toc378015428 \h 34(e) apply the concept of thermal energy transfer to everyday applications PAGEREF _Toc378015429 \h 3510. Temperature PAGEREF _Toc378015430 \h 36(a) explain how a physical property which varies with temperature, such as volume of liquid column, resistance of metal wire and electromotive force (e.m.f.) produced by junctions formed with wires of two different metals, may be used to define temperature scales PAGEREF _Toc378015431 \h 36(b) describe the process of calibration of a liquid-in-glass thermometer, including the need for fixed points such as the ice point and steam point PAGEREF _Toc378015432 \h 3611. Thermal Properties of Matter PAGEREF _Toc378015433 \h 37(a) describe a rise in temperature of a body in terms of an increase in its internal energy (random thermal energy) PAGEREF _Toc378015434 \h 37(b) define the terms heat capacity and specific heat capacity PAGEREF _Toc378015435 \h 37(c) recall and apply the relationship thermal energy = mass × specific heat capacity × change in temperature to new situations or to solve related problems PAGEREF _Toc378015436 \h 37(d) describe melting/solidification and boiling/condensation as processes of energy transfer without a change in temperature PAGEREF _Toc378015437 \h 38(e) explain the difference between boiling and evaporation PAGEREF _Toc378015438 \h 38(f) define the terms latent heat and specific latent heat PAGEREF _Toc378015439 \h 38(g) recall and apply the relationship thermal energy = mass × specific latent heat to new situations or to solve related problems PAGEREF _Toc378015440 \h 38(h) explain latent heat in terms of molecular behaviour PAGEREF _Toc378015441 \h 39(i) sketch and interpret a cooling curve PAGEREF _Toc378015442 \h 3912. General Wave Properties PAGEREF _Toc378015443 \h 41(a) describe what is meant by wave motion as illustrated by vibrations in ropes and springs and by waves in a ripple tank PAGEREF _Toc378015444 \h 41(b) show understanding that waves transfer energy without transferring matter PAGEREF _Toc378015445 \h 42(c) define speed, frequency, wavelength, period and amplitude PAGEREF _Toc378015446 \h 42(d) state what is meant by the term wavefront PAGEREF _Toc378015447 \h 43(e) recall and apply the relationship velocity = frequency × wavelength to new situations or to solve related problems PAGEREF _Toc378015448 \h 43(f) compare transverse and longitudinal waves and give suitable examples of each PAGEREF _Toc378015449 \h 4313. Light PAGEREF _Toc378015450 \h 44(a) recall and use the terms for reflection, including normal, angle of incidence and angle of reflection PAGEREF _Toc378015451 \h 44(b) state that, for reflection, the angle of incidence is equal to the angle of reflection and use this principle in constructions, measurements and calculations PAGEREF _Toc378015452 \h 44(c) recall and use the terms for refraction, including normal, angle of incidence and angle of refraction PAGEREF _Toc378015453 \h 45(d) recall and apply the relationship sin i / sin r = constant to new situations or to solve related problems (e) define refractive index of a medium in terms of the ratio of speed of light in vacuum and in the medium PAGEREF _Toc378015454 \h 45(f) explain the terms critical angle and total internal reflection PAGEREF _Toc378015455 \h 46(g) identify the main ideas in total internal reflection and apply them to the use of optical fibres in telecommunication and state the advantages of their use PAGEREF _Toc378015456 \h 46(h) describe the action of a thin lens (both converging and diverging) on a beam of light PAGEREF _Toc378015457 \h 47(i) define the term focal length for a converging lens PAGEREF _Toc378015458 \h 47(j) draw ray diagrams to illustrate the formation of real and virtual images of an object by a thin converging lens PAGEREF _Toc378015459 \h 4814. Electromagnetic Spectrum PAGEREF _Toc378015460 \h 49(a) state that all electromagnetic waves are transverse waves that travel with the same speed in vacuum and state the magnitude of this speed PAGEREF _Toc378015461 \h 49(b) describe the main components of the electromagnetic spectrum (c) state examples of the use of the following components: (i) radiowaves (e.g. radio and television communication) (ii) microwaves (e.g. microwave oven and satellite television) (iii) infra-red (e.g. infra-red remote controllers and intruder alarms) (iv) light (e.g. optical fibres for medical uses and telecommunications) (v) ultra-violet (e.g. sunbeds and sterilisation) (vi) X-rays (e.g. radiological and engineering applications) (vii) gamma rays (e.g. medical treatment) PAGEREF _Toc378015462 \h 50(d) describe the effects of absorbing electromagnetic waves, e.g. heating, ionisation and damage to living cells and tissue PAGEREF _Toc378015463 \h 5015. Sound PAGEREF _Toc378015464 \h 51(a) describe the production of sound by vibrating sources (b) describe the longitudinal nature of sound waves in terms of the processes of compression and rarefaction PAGEREF _Toc378015465 \h 51(c) explain that a medium is required in order to transmit sound waves and the speed of sound differs in air, liquids and solids PAGEREF _Toc378015466 \h 51(d) describe a direct method for the determination of the speed of sound in air and make the necessary calculation PAGEREF _Toc378015467 \h 51(e) relate loudness of a sound wave to its amplitude and pitch to its frequency PAGEREF _Toc378015468 \h 52(f) describe how the reflection of sound may produce an echo, and how this may be used for measuring distances PAGEREF _Toc378015469 \h 52(g) define ultrasound and describe one use of ultrasound, e.g. quality control and pre-natal scanning PAGEREF _Toc378015470 \h 5216. Static Electricity PAGEREF _Toc378015471 \h 54(a) state that there are positive and negative charges and that charge is measured in coulombs PAGEREF _Toc378015472 \h 54(b) state that unlike charges attract and like charges repel PAGEREF _Toc378015473 \h 54(c) describe an electric field as a region in which an electric charge experiences a force (d) draw the electric field of an isolated point charge and recall that the direction of the field lines gives the direction of the force acting on a positive test charge PAGEREF _Toc378015474 \h 54(e) draw the electric field pattern between two isolated point charges PAGEREF _Toc378015475 \h 55(f) show understanding that electrostatic charging by rubbing involves a transfer of electrons PAGEREF _Toc378015476 \h 55(g) describe experiments to show electrostatic charging by induction PAGEREF _Toc378015477 \h 56(h) describe examples where electrostatic charging may be a potential hazard PAGEREF _Toc378015478 \h 56(i) describe the use of electrostatic charging in a photocopier, and apply the use of electrostatic charging to new situations PAGEREF _Toc378015479 \h 5717. Current of Electricity PAGEREF _Toc378015480 \h 58(a) state that current is a rate of flow of charge and that it is measured in amperes PAGEREF _Toc378015481 \h 58(b) distinguish between conventional current and electron flow PAGEREF _Toc378015482 \h 58(c) recall and apply the relationship charge = current × time to new situations or to solve related problems PAGEREF _Toc378015483 \h 58(d) define electromotive force (e.m.f.) as the work done by a source in driving unit charge around a complete circuit PAGEREF _Toc378015484 \h 59(e) calculate the total e.m.f. where several sources are arranged in series PAGEREF _Toc378015485 \h 59(f) state that the e.m.f. of a source and the potential difference (p.d.) across a circuit component is measured in volts (g) define the p.d. across a component in a circuit as the work done to drive unit charge through the component PAGEREF _Toc378015486 \h 59(h) state the definition that resistance = p.d. / current (i) apply the relationship R = V/I to new situations or to solve related problems PAGEREF _Toc378015487 \h 59(j) describe an experiment to determine the resistance of a metallic conductor using a voltmeter and an ammeter, and make the necessary calculations PAGEREF _Toc378015488 \h 60(k) recall and apply the formulae for the effective resistance of a number of resistors in series and in parallel to new situations or to solve related problems PAGEREF _Toc378015489 \h 60(l) recall and apply the relationship of the proportionality between resistance and the length and cross-sectional area of a wire to new situations or to solve related problems PAGEREF _Toc378015490 \h 61(m) state Ohm’s Law PAGEREF _Toc378015491 \h 61(n) describe the effect of temperature increase on the resistance of a metallic conductor PAGEREF _Toc378015492 \h 61(o) sketch and interpret the I/V characteristic graphs for a metallic conductor at constant temperature, for a filament lamp and for a semiconductor diode PAGEREF _Toc378015493 \h 6218. D.C. Circuits PAGEREF _Toc378015494 \h 63(a) draw circuit diagrams with power sources (cell, battery, d.c. supply or a.c. supply), switches, lamps, resistors (fixed and variable), variable potential divider (potentiometer), fuses, ammeters and voltmeters, bells, light-dependent resistors, thermistors and light-emitting diodes PAGEREF _Toc378015495 \h 63(b) state that the current at every point in a series circuit is the same and apply the principle to new situations or to solve related problems (c) state that the sum of the potential differences in a series circuit is equal to the potential difference across the whole circuit and apply the principle to new situations or to solve related problems (d) state that the current from the source is the sum of the currents in the separate branches of a parallel circuit and apply the principle to new situations or to solve related problems (e) state that the potential difference across the separate branches of a parallel circuit is the same and apply the principle to new situations or to solve related problems PAGEREF _Toc378015496 \h 64(f) recall and apply the relevant relationships, including R = V/I and those for current, potential differences and resistors in series and in parallel circuits, in calculations involving a whole circuit PAGEREF _Toc378015497 \h 64(g) describe the action of a variable potential divider (potentiometer) PAGEREF _Toc378015498 \h 64(h) describe the action of thermistors and light-dependent resistors and explain their use as input transducers in potential dividers (i) solve simple circuit problems involving thermistors and light-dependent resistors PAGEREF _Toc378015499 \h 6419. Practical Electricity PAGEREF _Toc378015500 \h 65(a) describe the use of the heating effect of electricity in appliances such as electric kettles, ovens and heaters PAGEREF _Toc378015501 \h 65(b) recall and apply the relationships P = VI and E = VIt to new situations or to solve related problems PAGEREF _Toc378015502 \h 65(c) calculate the cost of using electrical appliances where the energy unit is the kW h PAGEREF _Toc378015503 \h 65(d) compare the use of non-renewable and renewable energy sources such as fossil fuels, nuclear energy, solar energy, wind energy and hydroelectric generation to generate electricity in terms of energy conversion efficiency, cost per kW h produced and environmental impact PAGEREF _Toc378015504 \h 66(e) state the hazards of using electricity in the following situations: (i) damaged insulation (ii) overheating of cables (iii) damp conditions PAGEREF _Toc378015505 \h 67(f) explain the use of fuses and circuit breakers in electrical circuits and of fuse ratings PAGEREF _Toc378015506 \h 67(g) explain the need for earthing metal cases and for double insulation PAGEREF _Toc378015507 \h 67(h) state the meaning of the terms live, neutral and earth PAGEREF _Toc378015508 \h 67(i) describe the wiring in a mains plug PAGEREF _Toc378015509 \h 68(j) explain why switches, fuses, and circuit breakers are wired into the live conductor PAGEREF _Toc378015510 \h 6820. Magnetism PAGEREF _Toc378015511 \h 69(a) state the properties of magnets PAGEREF _Toc378015512 \h 69(b) describe induced magnetism PAGEREF _Toc378015513 \h 69(c) describe electrical methods of magnetisation and demagnetisation PAGEREF _Toc378015514 \h 69(d) draw the magnetic field pattern around a bar magnet and between the poles of two bar magnets (e) describe the plotting of magnetic field lines with a compass PAGEREF _Toc378015515 \h 70(f) distinguish between the properties and uses of temporary magnets (e.g. iron) and permanent magnets (e.g. steel) PAGEREF _Toc378015516 \h 7021. Electromagnetism PAGEREF _Toc378015517 \h 71(a) draw the pattern of the magnetic field due to currents in straight wires and in solenoids and state the effect on the magnetic field of changing the magnitude and/or direction of the current PAGEREF _Toc378015518 \h 71(b) describe the application of the magnetic effect of a current in a circuit breaker PAGEREF _Toc378015519 \h 72(c) describe experiments to show the force on a current-carrying conductor, and on a beam of charged particles, in a magnetic field, including the effect of reversing (i) the current (ii) the direction of the field PAGEREF _Toc378015520 \h 73(d) deduce the relative directions of force, field and current when any two of these quantities are at right angles to each other using Fleming’s left-hand rule PAGEREF _Toc378015521 \h 74(e) describe the field patterns between currents in parallel conductors and relate these to the forces which exist between the conductors (excluding the Earth’s field) PAGEREF _Toc378015522 \h 74(f) explain how a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing (i) the number of turns on the coil (ii) the current PAGEREF _Toc378015523 \h 75(g) discuss how this turning effect is used in the action of an electric motor PAGEREF _Toc378015524 \h 75(h) describe the action of a split-ring commutator in a two-pole, single-coil motor and the effect of winding the coil on to a soft-iron cylinder PAGEREF _Toc378015525 \h 7622. Electromagnetic Induction PAGEREF _Toc378015526 \h 77(a) deduce from Faraday’s experiments on electromagnetic induction or other appropriate experiments: (i) that a changing magnetic field can induce an e.m.f. in a circuit (ii) that the direction of the induced e.m.f. opposes the change producing it PAGEREF _Toc378015527 \h 77(iii) the factors affecting the magnitude of the induced e.m.f. PAGEREF _Toc378015528 \h 78(b) describe a simple form of a.c. generator (rotating coil or rotating magnet) and the use of slip rings (where needed) (c) sketch a graph of voltage output against time for a simple a.c. generator PAGEREF _Toc378015529 \h 79(d) describe the use of a cathode-ray oscilloscope (c.r.o.) to display waveforms and to measure potential differences and short intervals of time (detailed circuits, structure and operation of the c.r.o. are not required) PAGEREF _Toc378015530 \h 80(e) interpret c.r.o. displays of waveforms, potential differences and time intervals to solve related problems PAGEREF _Toc378015531 \h 81(f) describe the structure and principle of operation of a simple iron-cored transformer as used for voltage transformations PAGEREF _Toc378015532 \h 82(g) recall and apply the equations VP / VS = NP / NS and VPIP = VSIS to new situations or to solve related problems (for an ideal transformer) PAGEREF _Toc378015533 \h 82(h) describe the energy loss in cables and deduce the advantages of high voltage transmission PAGEREF _Toc378015534 \h 82SECTION I: MEASUREMENTOverviewIn order to gain a better understanding of the physical world, scientists use a process of investigation that follows a general cycle of observation, hypothesis, deduction, test and revision, sometimes referred to as the scientific method. Galileo Galilei, one of the earliest architects of this method, believed that the study of science had a strong logical basis that involved precise definitions of terms and physical quantities, and a mathematical structure to express relationships between these physical quantities.In this section, we study a set of base physical quantities and units that can be used to derive all other physical quantities. These precisely defined quantities and units, with accompanying order-of-ten prefixes (e.g. milli, centi and kilo) can then be used to describe the interactions between objects in systems that range from celestial objects in space to sub-atomic particles.Extracted from PHYSICS GCE ORDINARY LEVEL (2014) Syllabus Document1. Physical Quantities, Units and MeasurementContentPhysical quantitiesSI unitsPrefixesScalars and vectorsMeasurement of length and timeLearning OutcomesCandidates should be able to:(a) show understanding that all physical quantities consist of a numerical magnitude and a unitTermDefinitionConstituentsPhysical quantityQuantity that can be measured[no need to remember this definition]A numerical magnitudeA unit(b) recall the following base quantities and their units: mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol)TermBase quantity (Derived quantities, e.g. area, are derived from base quantities, e.g. length)TypeMassLengthTimeCurrentTemperatureAmount of substanceSI unitkilogramsmetressecondsamperesKelvinmoleUnit symbolkgmsAKmol(c) use the following prefixes and their symbols to indicate decimal sub-multiples and multiples of the SI units: nano (n), micro (μ), milli (m), centi (c), deci (d), kilo (k), mega (M), giga (G)Magnitude+ve sign prefix (symbol)?ve sign prefix (symbol)Examples (where 1 ≤ y < 10)×10±1deca- (da)deci- (d)y kg = y ×103 gy cm = y ×10?2 my cm2 = y ×10?4 m2y cm3 = y ×10?6 m3y m = y ×102 cmy m2 = y ×104 cm2y m3 = y ×106 cm3×10±2hexa- (h)centi- (c)×10±3kilo- (k)milli- (m)×10±6mega- (M)micro- (?)×10±9giga- (G)nano- (n)(d) show an understanding of the orders of magnitude of the sizes of common objects ranging from a typical atom to the EarthObjectH atomChopsticks lengthFootball field lengthMount Everest’s heightEarth’s radiusMagnitude110?15 m210?1 m1102 m8.848103 m6.378106 mNote: There is no need to remember these magnitudes, an appreciation will do(e) state what is meant by scalar and vector quantities and give common examples of eachTermDefinitionScalar quantityPhysical quantities that have magnitude onlyVector quantityPhysical quantities that possess both magnitude and directionExamplesScalarVectorDistanceDisplacementSpeedVelocityEnergyForceMassWeight(f) add two vectors to determine a resultant by a graphical methodDetermination of resultant forceCaseCase 1:Parallel vectorsCase 2: Non-parallel vectorsCase 2a: Same originCase 2b: Tip-to-tail74128173025002755907302500161290736600045759951435006978658513700106489514138000693420111760001082941124130065468586360001026160-19050065278010160000100330064100StepsCalculate resultant forceWrite down the scale using 1 cm : ? N (scale must allow diagram drawn to be more than half of the space given in question)Draw the 2 forces with single arrows according to the scaleFinish the parallelogram with dotted lines using set squareDraw resultant force from the origin with a double arrowMeasure length of resultant forceCalculate resultant forceWrite down the scale using 1 cm : ? N (scale must allow diagram drawn to be more than half of the space given in question)Draw the 2 forces with single arrows according to the scaleDraw resultant force from the start to end of the 2 forces with a double arrowMeasure length of resultant forceCalculate resultant forceExample 3N 5N73533012977600129310128472004311651090480024701512636500Resultant force= 5N ? 3N= 2N in the forward directionScale: 1 cm : 0.5 N568960660405 N5 N10029831373197 N7 N422910142875008261354330700010934705016500669290633095007893052057400040640062738000317500250190008593149080518o18o655479040o40o75834953499005246691225550010642601778000100330036830007602548445520o20o61785516986001754568699500424180528643 N3 NResultant force= 3.5 ÷ 0.5= 7 N, acting 18o to the horizontalScale: 1 cm : 0.5 N1152329105410007304281092885 N5 N12897191104904.4 N4.4 N1012825596900062992048133000541020104140001249680144780008547106868740o40o74686712001500122852978105009626608224320o20o77437222860005696611378273 N03 N121994211811076o76o256540893390080264016203001122680438150032766013124900Resultant force= 3.5 ÷ 0.5= 7 N, acting 76o to the horizontal(g) describe how to measure a variety of lengths with appropriate accuracy by means of tapes, rules, micrometers and calipers, using a vernier scale as necessary#InstrumentPrecisionPurposeMethod of measurementPossible error1Tape10?1 cmTo measure widths (e.g. long distances)Position eye directly above the markings on the tape when making measurement to avoid parallax errorParallax error2Metre rule10?1 cmTo measure depths (e.g. of ponds)Measure from a randomly chosen point instead of the ends to avoid zero error (from wear and tear)Substract the reading at the start of the object from the reading at the end of the objectParallax error3Caliper10?1 cmTo measure circular objects To measure cylindersCircular objectsUse jaws of the external calipers to grip the widest part of the circular objectDistance between jaws is measured with a metre ruleCylindersInvert the jaws to use the internal calipersUse jaws of the internal calipers to measure the inner diameter of the cylinderDistance between jaws is measured with a metre ruleParallax error4Vernier caliper10?2 cmTo measure the internal and external diameters of an objectConsists of a main scale and a sliding vernier scaleGrip the object using the correct pair of jawsRead the main scale directly opposite the zero mark on the vernier scale (e.g. 2.4 cm)Read the vernier mark that coincides with a marking on the main scale (e.g. +0.03 cm)Close the vernier caliper to check for zero error to be corrected (e.g. +0.02 cm)Calculate the final reading by adding the vernier reading and substracting the zero error [e.g. 2.4 + (+0.03) ? (+0.02) = 2.41 cm]Zero error5Micrometer screw gauge10?3 cmTo measure the external diameter of small precision (e.g. wires, ball bearings)Turn the thimble such that the object is gripped gentlyTurn the ratchet until it starts to clickRead the main scale reading at the edge of the thimble (e.g. 6.5 mm)Read the thimble scale reading (reading 35 indicates 0.35 mm)Close the micrometer screw guage to check for zero error to be corrected (e.g. +0.02 mm)Calculate the final reading by adding the vernier reading and substracting the zero error [e.g. 6.5 + (+0.35) ? (+0.02) = 6.65 cm]Zero errorNote: This is mainly important for practical sessions(h) describe how to measure a short interval of time including the period of a simple pendulum with appropriate accuracy using stopwatches or appropriate instrumentsTermMeaning as for a pendulumOscillationEach complete to-and-fro motion of the pendulum bobPeriodTime taken for one complete oscillationInstrumentPrecisionMethod of measurement of pendulum periodFactors affecting period of the pendulumPossible errorStopwatch10?2 sMeasure the time taken for the pendulum to make 20 oscillationsFind the period accurately by dividing the total time by 20Length of string affects the periodMass of bob does not affect the periodHuman reaction time (about 0.3 to 0.5 s)Note: This is mainly important for practical sessionsSECTION II: NEWTONIAN MECHANICSOverviewMechanics is the branch of physics that deals with the study of motion and its causes. Through a careful process of observation and experimentation, Galileo Galilei used experiments to overturn Aristotle’s ideas of the motion of objects, for example the flawed idea that heavy objects fall faster than lighter ones, which dominated physics for about 2,000 years.The greatest contribution to the development of mechanics is by one of the greatest physicists of all time, Isaac Newton. By extending Galileo’s methods and understanding of motion and gravitation, Newton developed the three laws of motion and his law of universal gravitation, and successfully applied them to both terrestrial and celestial systems to predict and explain phenomena. He showed that nature is governed by a few special rules or laws that can be expressed in mathematical formulae. Newton’s combination of logical experimentation and mathematical analysis shaped the way science has been done ever since.In this section, we begin by examining kinematics, which is a study of motion without regard for the cause. After which, we study the conditions required for an object to be accelerated and introduce the concept of forces through Newton’s Laws. Subsequently, concepts of moments and pressure are introduced as consequences of a force. Finally, this section rounds up by leading the discussion from force to work and energy, and the use of the principle of conservation of energy to explain interactions between bodies.Extracted from PHYSICS GCE ORDINARY LEVEL (2014) Syllabus Document2. KinematicsContentSpeed, velocity and accelerationGraphical analysis of motionFree-fallEffect of air resistanceLearning OutcomesCandidates should be able to:(a) state what is meant by speed and velocityTermDefinitionAverage speedTotal distance travelled per unit timeVelocityChange in displacement per unit time(b) calculate average speed using distance travelled / time takenTermFormulaAverage speed (c) state what is meant by uniform acceleration and calculate the value of an acceleration using change in velocity / time takenCommonlegendKeytauvsTermTime takenAccelerationInitial velocityFinal velocityDisplacementTermDefinitionFormulaeAccelerationChange in velocity per unit time Uniform accelerationConstant change in velocity per unit timeN.A.Related formulae to find accelerationGivenFormula to useTime taken & Final velocity Time taken & Displacement Final velocity & Displacement (d) interpret given examples of non-uniform accelerationNon-uniform accelerationUniform accelerationIncreasing accelerationDecreasing accelerationPushing on the pedalReleasing force on the pedalNo change in force exerted on the pedal(e.g. pushing the pedal all the way)(e) plot and interpret a displacement-time graph and a velocity-time graphDifferencesDisplacement-time graphVelocity-time graphLabel of y-axisDisplacement / mVelocity / m s-1Label of x-axisTime / sTime / sArea below graphN.A.Total displacement / mGradient of graphVelocity / m s-1Acceleration / m s-2(f) deduce from the shape of a displacement-time graph when a body is: (i) at rest (ii) moving with uniform velocity (iii) moving with non-uniform velocityDisplacement-time graphScenariosDisplacementGradientAt restZero displacement N.A.Moving with uniform velocityIncreasing displacementConstant gradientMoving with non-uniform velocityVarying displacementVarying gradient(g) deduce from the shape of a velocity-time graph when a body is: (i) at rest (ii) moving with uniform velocity (iii) moving with uniform acceleration (iv) moving with non-uniform accelerationVelocity-time graphScenariosVelocityGradientAt restZero velocityN.A.Moving with uniform velocityConstant velocityZero gradientMoving with uniform accelerationIncreasing velocityConstant gradientMoving with non-uniform accelerationVarying velocityVarying gradient(h) calculate the area under a velocity-time graph to determine the displacement travelled for motion with uniform velocity or uniform accelerationTermFormulaeDisplacement TermFormulae in symbolsDisplacement Average velocity (i) state that the acceleration of free fall for a body near to the Earth is constant and is approximately 10 m/s2Relationship between force and accelerationWhen a force is exerted on an object, the object will experience constant acceleration in the direction of the force if there is no other force acting against it (i.e. constant resultant force)Any free falling object near to the Earth will experience constant acceleration of approximately 10 m/s2 due to gravity as there is no air resistance acting against itAcceleration will only decrease when the object enters Earth as it will then experience air resistance(j) describe the motion of bodies with constant weight falling with or without air resistance, including reference to terminal velocityDifferencesWith air resistanceWithout air resistanceDescription of motion of bodies with constant weightAs an object falls in air,it increases its speed with an initial acceleration of 10ms-2Air resistance opposing weight increases as speed increases,causing resultant force and hence acceleration to decreaseWhen air resistance is equal to the weight of the body,the forces balance out to zero resultant force causing zero acceleration and the object travels at constant terminal velocityAs an object falls in a vacuum,it increases its speed with an uniform acceleration of 10ms-2This is because there is no air resistance present,thus resultant force is constantGraph of velocity against time3. DynamicsContentBalanced and unbalanced forcesFree-body diagramFrictionLearning OutcomesCandidates should be able to:(a) apply Newton's Laws to: (i) describe the effect of balanced and unbalanced forces on a body (ii) describe the ways in which a force may change the motion of a body (iii) identify action-reaction pairs acting on two interacting bodies (stating of Newton's Laws is not required)ScenariosDescriptionPossible effectsConditionBalanced forces on a bodyResultant force is equal to 0 NObject at restObject initially at restObject travels at constant speed in a straight lineObject initally in motionUnbalanced forces on a bodyResultant force is more than 0 NObject acceleratesObject is initially at restor Force in same direction as object’s motionObject deceleratesForce in opposite direction to object’s motionObject changes directionForce acts at an angle to object’s motionIllustrations of unbalanced forcesObject acceleratesObject deceleratesObject changes direction103949524892000104521050355500TermMeaningExampleRelationshipAction forceThe force a body (body 1) exerts on another body (body 2)Feet of a swimmer pushing against the swimming pool wallForces always occur in pairs, each made up of a action force and a reaction forceAction and reaction forces are equal in magnitude,act in opposite directions andon 2 different bodiesReaction forceThe subsequent force body 2 exerts on body 1 in reaction to the action forceForce that propels in swimmer forward in reaction(b) identify forces acting on an object and draw free body diagram(s) representing the forces acting on the object (for cases involving forces acting in at most 2 dimensions)LegendKeyTermExplanationTThrustN.A.WWeight of objectDue to gravityFForceN.A.+FContact forceReaction force due to weight of object*fFrictionBetween object and groundRAir resistanceFriction between object and air moleculesAir resistance applicableObject thrust upwards Object released high up Without air resistanceWith air resistanceAir resistance not applicableObject on the ground Object pushed on the ground (c) solve problems for a static point mass under the action of 3 forces for 2-dimensional cases (a graphical method would suffice)ReferencesRefer to Learning Outcome 1(f) on Page 13(d) recall and apply the relationship resultant force = mass × acceleration to new situations or to solve related problemsTermFormulaSI unitsInterpretationResultant force FmaA resultant force of 2 N exerted on a body of mass 0.5 kg causes the body to accelerate at 4 m s-2Nkgm s-2(e) explain the effects of friction on the motion of a bodyScenarioPossible motionsExplanationBox rests on a flat horizontal floorBox remains at restThere is no frictional force acting on the boxContact force of the ground is equal to the weight of the box due to gravityBox slides along a rough tableDecelerates and eventually stopsFrictional force opposes the force of the motionKinetic energy is converted to heat energyBox rests on a slopeBox remains at restDownward force of attraction acting on the box due to gravity is equal to the upward frictional forceResultant force is zeroBox accelerates down the slopeDownward force of attraction acting on the box due to gravity is more than the upward frictional forceResultant force is more than zero4. Mass, Weight and DensityContentMass and weightGravitational field and field strengthDensityLearning OutcomesCandidates should be able to:(a) state that mass is a measure of the amount of substance in a body (b) state that mass of a body resists a change in the state of rest or motion of the body (inertia)TermDefinitionMassMeasure of the amount of substance in a body which resists a change in the state of rest or motion of the bodyInertiaThe resistance of a body with mass to start moving if it is stationary or stop moving if it is in motion in its first instance(c) state that a gravitational field is a region in which a mass experiences a force due to gravitational attractionTermDefinitionGravitational fieldA region in which a mass experiences a force due to gravitational attraction(d) define gravitational field strength, g, as gravitational force per unit massTermDefinitionGravitational field strengthGravitational force acting per unit mass on an objectThe gravitational field strength on Earth is about 10 N kg-1(e) recall and apply the relationship weight = mass × gravitational field strength to new situations or to solve related problemsTermDefinitionFormulaSI unitsInterpretationWeightThe force of attraction on an object due to gravity g on Earth is about 10 N kg-1WmgA 2 kg mass has a weight of 20 N due to Earth’s gravitational pull of 10 N kg-1kgNN kg-1(f) distinguish between mass and weightDifferencesMassWeightMeaningAmount of matter in a bodyDue to pull of gravity on a bodyScalar or vectorScalar; has only magnitudeVector; has both magnitude and directionUnitMeasured in kg (kilograms)Measures in N (newtons)VariationsConstant regardless of gravitational field strengthVaries according to gravitational field strength(g) recall and apply the relationship density = mass / volume to new situations or to solve related problemsTermDefinitionFormulaSI unitsInterpretationDensityMass per unit volume mVAn object with mass of 4 kg and volume of 2 m3 has a density of 2 kg m-3kg m-3kgm35. Turning Effect of ForcesContentMomentsCentre of gravityStabilityLearning OutcomesCandidates should be able to:(a) describe the moment of a force in terms of its turning effect and relate this to everyday examples (b) recall and apply the relationship moment of a force (or torque) = force × perpendicular distance from the pivot to new situations or to solve related problemsTermDefinitionTurning effectThe turning of an object about a pivotThe greater the moment, the greater the object turns about the pivotTermDefinitionFormulaSI unitsInterpretationMoment of a forceThe product of the force and the perpendicular distance between the line of action of the force and a pivot, and resulting in a turning effect MomentFpdA force of 2 N acting with a perpendicular distance of 2 m produces a moment of 4 NmNmNm(c) state the principle of moments for a body in equilibrium (d) apply the principle of moments to new situations or to solve related problemsTermDefinitionFormulaPrinciple of momentsWhen an object is in equilibrium, the sum of clockwise moments about a pivot is equal to sum of anticlockwise moments about the same pivot (e) show understanding that the weight of a body may be taken as acting at a single point known as its centre of gravityTermDefinitionAlternative definitionCentre of gravity of an objectPoint of application of the resultant force on an object exerted by gravity for any orientation of the objectPoint through which the whole weight of an object appears to act for any orientation of the object (f) describe qualitatively the effect of the position of the centre of gravity on the stability of objectsScenarioEffect on stabilityMeasure to increase stabilityHigher centre of gravityLower stability of the objectToppling will occur at smaller angles of tiltDecrease the centre of gravity by adding more mass below the current centre of gravity to the objectObject is tilted such that centre of gravity is still vertically above the base of objectObject will not toppleIncrease the size of baseObject is tilted such that centre of gravity is no longer vertically above the base of objectObject will topple6. PressureContentPressurePressure differencesPressure measurementLearning OutcomesCandidates should be able to:(a) define the term pressure in terms of force and area (b) recall and apply the relationship pressure = force / area to new situations or to solve related problemsTermDefinitionFormulaSI unitsInterpretationPressureAverage force per unit area pFAA force of 4 N acting on an area of 2 m2 results in a pressure of 2 PaPa or N m-2Nm2(c) describe and explain the transmission of pressure in hydraulic systems with particular reference to the hydraulic pressTransmission of pressure in hydraulic systemsDescriptionOil is the incompressible, high density liquid used in the transmission of pressureEffort piston has a smaller cross sectional area than that of the piston below the loadSince liquid pressure at both pistons are equal when they are at the same level,A small force exerted on the effort piston will create a much bigger force on the load piston in comparisonDiagramCalculations383540716280oil00oilSince water level at X is the same as the water level at Y, Since If the load is at Y and FY represents the weight of the load, use of the hydraulic press will require a smaller force of FX instead of FY to lift the load upwards(d) recall and apply the relationship pressure due to a liquid column = height of column × density of the liquid × gravitational field strength to new situations or to solve related problemsTermFormulaSI unitsPressuredue toliquidcolumn phgN m-2mkg m-3N kg-1Example of diagram of manometerCalculations1630680-14605gas00gas187261531305500Water level at A is the same as the water level at B (e) describe how the height of a liquid column may be used to measure the atmospheric pressure Diagram of barometerDescription of measurement of atmospheric pressureSet up a barometer using high density mercury of 13.6 kg m-3 (f) describe the use of a manometer in the measurement of pressure differenceRedirect instructionsRefer to Learning Outcome 6(f) above7. Energy, Work and PowerContentEnergy conversion and conservationWorkPowerLearning OutcomesCandidates should be able to:(a) show understanding that kinetic energy, potential energy (chemical, gravitational, elastic), light energy, thermal energy, electrical energy and nuclear energy are examples of different forms of energyExamples of forms of energyKineticPotentialThermalLightElectricalNuclearMovementStored energyHeatChemicalGravitationalElasticFood or batteriesRaised above groundCompression or stretching of elastic objects like springs(b) state the principle of the conservation of energy and apply the principle to new situations or to solve related problemsTermDefinitionPrinciple of conservation of energyEnergy can neither be created nor destroyed but can only be transferred from one body to another or from one form to another while total energy remains the same(c) calculate the efficiency of an energy conversion using the formula efficiency = energy converted to useful output / total energy inputTermFormulaEnergy input Efficiency (d) state that kinetic energy Ek = ? mv2 and gravitational potential energy Ep = mgh (for potential energy changes near the Earth’s surface) (e) apply the relationships for kinetic energy and potential energy to new situations or to solve related problemsTermFormulaSI unitsKinetic energyof an object EkmvJkgm s-1Potential energyof an object EpmghJkgN kg-1m(f) recall and apply the relationship work done = force × distance moved in the direction of the force to new situations or to solve related problemsTermFormulaSI unitsWork doneof an object WFdJNm(g) recall and apply the relationship power = work done / time taken to new situations or to solve related problemsTermFormulaSI unitsPower ofan object PWEtW or J s-1JJsSECTION III: THERMAL PHYSICSOverviewAmongst the early scientists, heat was thought as some kind of invisible, massless fluid called ‘caloric’. Certain objects that released heat upon combustion were thought to be able to ‘store’ the fluid. However, this explanation failed to explain why friction was able to produce heat. In the 1840s, James Prescott Joule used a falling weight to drive an electrical generator that heated a wire immersed in water. This experiment demonstrated that work done by a falling object could be converted to heat.In the previous section, we studied about energy and its conversion. Many energy conversion processes which involve friction will have heat as a product. This section begins with the introduction of the kinetic model of matter. This model is then used to explain and predict the physical properties and changes of matter at the molecular level in relation to heat or thermal energy transfer.Extracted from PHYSICS GCE ORDINARY LEVEL (2014) Syllabus Document8. Kinetic Model of MatterContentStates of matterBrownian motionKinetic modelLearning OutcomesCandidates should be able to:(a) compare the properties of solids, liquids and gasesPropertiesSolidsLiquidsGasesVolumeFixedFixedNot fixedShape FixedNot fixedNot fixedCompressibilityNoNoYesDensityHighHighLowOthersUsually hard and rigidTend to form dropletsN.A.(b) describe qualitatively the molecular structure of solids, liquids and gases, relating their properties to the forces and distances between molecules and to the motion of the moleculesMolecular structureSolidsLiquidsGasesForces of attraction between particlesParticles held by very strong forces of attractionParticles held by strong forces of attractionParticles held by weak forces of attractionDistance between particles Packed very closely together with more particles per unit volumePacked close to one anotherSpread far apart from one anotherMotion of particlesVibrate about fixed positionsSlide and move past one another randomlyMove in a constant, random and erratic manner(c) infer from Brownian motion experiment the evidence for the movement of moleculesTermDefinitionBrownian motion experimentSetupObservationsInferencesBrownian motionSmall particles suspended in a liquid or gas tend to move in random paths through the fluid even if it is calmPlace smoke particles in a container of air, suspending them in airSmoke particles are being continuously bombarded by air molecules and move irregularly by Brownian motionThis shows that the fluids have an ability to flow or move freely(d) describe the relationship between the motion of molecules and temperatureRelationship between motion of molecules and temperatureWhen solid or fluid (liquid / gas) is at a higher temperature, the particles vibrate or move faster respectivelyThe average kinetic energy of the particles is the measure of temperature or degree of hotness(e) explain the pressure of a gas in terms of the motion of its moleculesExplanation of pressure of a gasEffect of increasing temperature on pressureMolecules present in a fluid collide with the walls of the container at a constant rate Each collision exerts a force on the walls of the containerAs the force is acted on a particular quantity of surface area of walls, the gas exerts pressure on the wallsWhen temperature is increased, molecules move faster and collide with the walls of the container more frequently Average force on the walls of the container increases over the same surface area of walls, thus gas pressure increases(f) recall and explain the following relationships using the kinetic model (stating of the corresponding gas laws is not required): (i) a change in pressure of a fixed mass of gas at constant volume is caused by a change in temperature of the gas (ii) a change in volume occupied by a fixed mass of gas at constant pressure is caused by a change in temperature of the gas (iii) a change in pressure of a fixed mass of gas at constant temperature is caused by a change in volume of the gasGas equation CauseTemperature of gas increasesVolume decreasesEffectVolume increasesPressure unchangedPressure increasesPressure increasesConditionOnly if container can expand furtherOnly if container can expand furtherOnly if container cannot expandUnder all casesExplanationMolecules gain kinetic energy and move fasterGas molecules hit the container walls with higher speedFrequency of collisions of the gas molecules with the walls increasesGreater force is exerted on walls, gas expands since container can expandGas expands in volume since the container can expand, decreasing the number of gas particles per unit volume and increasing surface area of wallsNumber of gas particles hitting the walls per unit area decreasesAverage force exerted per unit area remains unchanged, hence a constant pressure is maintainedMolecules gain kinetic energy and move fasterGas molecules hit the container walls with higher speedFrequency of collisions of the gas molecules with the walls increasesAverage force exerted per unit area on the container walls increasesGas is compressed at constant temperature and number of gas particles per unit volume increasesFrequency of collisions of molecules with container walls increasesForce exerted per unit area on the container increases, thus pressure increases(g) use the relationships in (f) in related situations and to solve problems (a qualitative treatment would suffice)9. Transfer of Thermal EnergyContentConductionConvectionRadiationLearning OutcomesCandidates should be able to:(a) show understanding that thermal energy is transferred from a region of higher temperature to a region of lower temperatureThermal energy transferThermal energy is transferred from a region of higher temperature to a region of lower temperature(b) describe, in molecular terms, how energy transfer occurs in solidsEnergy transfer occurs in solidsIn comparison with fluidsWhen one region of a solid is heated, the molecules there gain kinetic energy and vibrate fasterThey collide with the slower neighbouring particles and transfer energy to themIn fluids, the particles are further apart from each another than in liquids or gasesTherefore kinetic energy is transferred more slowly(c) describe, in terms of density changes, convection in fluidsConvection in fluidsIn comparison with solidsHot fluid expands and has lower density than cold fluid, causing it to riseCold fluid contracts and has higher density than hot fluids, sinking to replace the hot fluidConvection current is set up when the cycle repeatsConvection involves the bulk movement of fluids which carry heat with themSolids cannot cause convection as heat can only be transferred from one molecule to anotherThe molecules are unable to flow around themselves(d) explain that energy transfer of a body by radiation does not require a material medium and the rate of energy transfer is affected by: (i) colour and texture of the surface (ii) surface temperature (iii) surface areaEnergy transfer of a body by radiationInfrared radiation is continuously emitted by all objects through their surfaces as radiation does not require a material medium for thermal transfer to occurWhen these infrared waves reach another object, the waves are transformed into heat energy, which is then absorbed by the objectHigher surface areas, higher surface temperatures (relative to surroundings) and dull surfaces accelerate radiation of heat(e) apply the concept of thermal energy transfer to everyday applicationsApplicationsFeaturesAdvantagesReasonsStyrofoam food packagesMostly made of styrofoamConduction is reducedThis is due to the presence of many air pocketsAir is a poor conductor of heatCovered with a lidConvection is reducedConvection currents are unable to be set up due to the presence of the lid compressing the contents into a closely packed arrangementVacuum flasksPlastic stopperConduction & convection is reducedPlastic is a poor conductor of heatWith a stopper, a convection current is being prevented from set upVacuum between the glass wallsAs vacuum is unable to conduct and cause convection of heat, the amount of heat medium is decreasedSilvered glass wallsRadiation is reducedThe shiny and smooth surface is a poor emitter and absorber of heatIt is able to reflect heat back to the container very wellAir trapped above contentsConduction is reducedAir is a poor conductor of heat10. TemperatureContentPrinciples of thermometryLearning OutcomesCandidates should be able to:(a) explain how a physical property which varies with temperature, such as volume of liquid column, resistance of metal wire and electromotive force (e.m.f.) produced by junctions formed with wires of two different metals, may be used to define temperature scalesDifferencesMercury thermometerPlatinum wireThermocouplePhysical propertyVolume or height of liquid columnResistance Electromotive force (e.m.f.) produced by 2 junctions formed with wires of 2 different metalsRationaleMercury is sensitive to changes in temperature and expands when temperature risesResistance of the wire rises when temperature rises E.m.f. between two substances increases when the temperature difference between them risesApparatus1388110227965Copper 00Copper 4953001803400015855951803400049911017970500-26035274320Copper0oCs 00Copper0oCs 88074589535mV00mV948055850900013138155518150011988806508750065151063627000220345551815002184405530850076517556959500827405362585Iron 00Iron Calculations (b) describe the process of calibration of a liquid-in-glass thermometer, including the need for fixed points such as the ice point and steam pointCalibration of liquid-in-glass thermometerNeed for fixed pointsPlace thermometer in ice point (funnel containing pure melting ice), then in steam point (above boiling water)Mark the level of mercury in both situationsThe difference in temperature of both points is 100oCBetween the upper and lower fixed points markings, divide and mark one hundred equal divisionsSince an increase in the temperature will increase the volume of mercury proportionately, each division is one degree CelsiusFixed points (ice and steam points) are used for calibration for all thermometers to agree accurately on a same temperature scaleThis is because fixed points are reproducible and will produce definite temperatures 11. Thermal Properties of MatterContentInternal energySpecific heat capacityMelting, boiling and evaporationSpecific latent heatLearning OutcomesCandidates should be able to:(a) describe a rise in temperature of a body in terms of an increase in its internal energy (random thermal energy)TermMeaningInternal energyRandom thermal energy of a body resulting from the kinetic and potential energy of the particles by their movement and arrangementDescription of rise in temperature of a bodyWhen a body is heated, its internal energy (consisting of kinetic energy and potential energy) risesKinetic energyPotential energyKinetic energy of particles increases, causing particles vibrate or move fasterDuring melting and boiling, potential energy of the particles also increasesThis is since there is no rise in temperature, causing latent heat to betaken in(b) define the terms heat capacity and specific heat capacityTermDefinitionSymbolHeat capacityAmount of heat energy required to raise the temperature of a body by 1 K or 1 °CCSpecific heat capacityAmount of heat energy required to raise the temperature of 1 kg of a body by 1 K or 1 °Cc(c) recall and apply the relationship thermal energy = mass × specific heat capacity × change in temperature to new situations or to solve related problemsTermFormulaSI unitsThermal energy when there is a temperature change mckgJ kg-1 oC-1orJ kg-1 K-1oCorK(d) describe melting/solidification and boiling/condensation as processes of energy transfer without a change in temperatureTermMeaningMeltingProcess of energy transfer from the surroundings to a solid to turn it to a liquid without a change in temperatureSolidificationProcess of energy transfer from a liquid to the surroundings to turn it to a solid without a change in temperatureBoilingProcess of energy transfer from the surroundings to a liquid to turn it to a gas without a change in temperatureCondensationProcess of energy transfer from a gas to the surroundings to turn it to a liquid without a change in temperature(e) explain the difference between boiling and evaporationDescription of evaporationAt any temperature, the molecules of liquid are in continuous random motion with different speedsSome more energetic molecules near to the surface of the liquid have enough energy to overcome the attractive forces of other molecules and escapeThey evaporate from the liquid to form a vapourDifferencesBoilingEvaporationTemperatureOccurs at a fixed temperature Occurs at any temperatureLocationOccurs throughout the liquidOccurs at the surface of the liquidHeat sourceHeat is supplied from an energy sourceHeat is supplied by the surroundings(f) define the terms latent heat and specific latent heatTermDefinitionLatent heatHeat energy released or absorbed during a change of state to make or break intermolecular forces of attraction without any change in temperatureLatent heat of fusionHeat energy required to change a solid to its liquid state or vice versa without any change in temperatureLatent heat of vapourisationHeat energy required to change a liquid to its vapour state or vice versa without any change in temperatureSpecific latent heatHeat energy required to change 1 kg of a substance from one state to another or vice versa without any change in temperature(g) recall and apply the relationship thermal energy = mass × specific latent heat to new situations or to solve related problemsTermFormulaSI unitsThermal energy when thereis no temperature change mkgJ kg-1(h) explain latent heat in terms of molecular behaviourTermDefinitionLatent heatHeat energy released or absorbed during a change of state to make or break intermolecular forces of attraction without any change in temperature(i) sketch and interpret a cooling curveSketch of cooling curve of waterInterpretation of cooling curve-19822177078900685165190602400812165174569condensation00condensationDescriptionExplanationDecreases in temperature during gas, liquid and solid state in the graphThis is because thermal energy is being released with no change in intermolecular forces of attraction between the moleculesNo change in temperature during condensation and freezing until all the water vapour has condensed and all the water has frozenThis is because thermal energy is being released to form greater intermolecular forces of attraction between the molecules such that there is a state changeSECTION IV: WAVESOverviewWaves are inherent in our everyday lives. Much of our understanding of wave phenomena has been accumulated over the centuries through the study of light (optics) and sound (acoustics). The nature of oscillations in light was only understood when James Clerk Maxwell, in his unification of electricity, magnetism and electromagnetic waves, stated that all electromagnetic fields spread in the form of waves.Using a mathematical model (Maxwell’s equations), he calculated the speed of electromagnetic waves and found it to be close to the speed of light, leading him to make a bold but correct inference that light consists of propagating electromagnetic disturbances. This gave the very nature of electromagnetic waves, and hence its name.In this section, we examine the nature of waves in terms of the coordinated movement of particles. The discussion moves on to wave propagation and its uses by studying the properties of light, electromagnetic waves and sound, as well as their applications in wireless communication, home appliances, medicine and industry.Extracted from PHYSICS GCE ORDINARY LEVEL (2014) Syllabus Document12. General Wave PropertiesContentDescribing wave motionWave termsLongitudinal and transverse wavesLearning OutcomesCandidates should be able to:(a) describe what is meant by wave motion as illustrated by vibrations in ropes and springs and by waves in a ripple tankTermDefinitionWave motionPropagation of waves through a medium by the vibration of particles in the wave transmitting energyIllustrationsTransverse wavesLongitudinal wavesRope222186583502500215455590614500163068098044000N.A.SpringRipple tank22606001687195002226310-381000N.A.-825557848500153670-4318000Comparison of waves in a ripple tankDescriptionWaves of water undergo refraction when it travels from deeper water to shallower water or vice versaDifferencesDeeper waterShallower waterIllustrationsWavelengthIncreasesDecreasesVelocityIncreasesDecreasesFrequencyRemains the sameRemains the sameDirectionAway from the normalTowards the normalWavefrontPerpendicular to direction of wavePerpendicular to direction of wave(b) show understanding that waves transfer energy without transferring matterWavesA wave is the collective motion of many particlesOccurs when particles of the medium move in a specific mannerWhat is transferredWhat is not transferredEnergyMedium(c) define speed, frequency, wavelength, period and amplitudeTermDefinitionFormulaFrequencyThe number of complete waves produced per second by a source PeriodThe time taken to produce one complete wave WavelengthShortest distance between any two points of a wave in phase SpeedDistance travelled by a crest or rarefraction per unit time by a wave AmplitudeMaximum displacement of crest or rarefaction from the rest positionRefer to diagramDiagram(d) state what is meant by the term wavefrontTermDefinitionWavefrontImaginary line on a wave that joins all points that are in the same phase(e) recall and apply the relationship velocity = frequency × wavelength to new situations or to solve related problemsTermFormulaSI unitsVelocity of wave vfm s-1Hzm(f) compare transverse and longitudinal waves and give suitable examples of eachTermDefinitionPropertiesTransverse waveWaves that travel in a direction perpendicular to the direction of vibration of the particlesCrests and troughs represent amplitude and minimum displacement respectivelyLongitudinal waveWaves that travel in a direction parallel to the direction of vibration of the particlesRarefactions and compressions represent amplitude and minimum displacement respectively13. LightContentReflection of lightRefraction of lightThin lensesLearning OutcomesCandidates should be able to:(a) recall and use the terms for reflection, including normal, angle of incidence and angle of reflectionRay diagramLegend905922-1524000mirrori represents theangle of incidencer represents theangle of reflection (b) state that, for reflection, the angle of incidence is equal to the angle of reflection and use this principle in constructions, measurements and calculationsReflection lawsFeatures of a plane mirror imageAngle of incidence is equal to angle of reflectionThe normal, incident ray and reflected ray all lie in the same planeFeaturesAcronymVirtualImage is the same size as the object (Size)Image as far away from the mirror as the object is from the mirror (Far)Laterally invertedUprightVS FLU(c) recall and use the terms for refraction, including normal, angle of incidence and angle of refractionTermMeaningConditionsRemarkRefractionRefers to the change in direction or bending of light when it passes from one medium to another medium of different optical densities due to the change in speed of lightThe light ray bends towards the normal when travelling into a medium of higher optical density The light ray bends away from the normal when travelling into a medium of lower optical density Angle of incidence must not be 0oIf ray travels from a denser to less dense medium, angle of incidence must be less than critical angle ‘Density’ in this caserepresents opticaldensityRay diagramReal and apparent depthLegendi represents the angle of incidencer represents the angle of refraction(d) recall and apply the relationship sin i / sin r = constant to new situations or to solve related problems (e) define refractive index of a medium in terms of the ratio of speed of light in vacuum and in the mediumTermDefinitionFormulaLegendRefractive index of a mediumThe constant ratio of the speed of light in vacuum to the speed of light in the medium n represents refractive indexi represents the angle of incidencer represents the angle of refraction(f) explain the terms critical angle and total internal reflectionTermDefinitionFormulaCritical angleThe angle of incidence of a ray in the optically denser medium whereby the angle of refraction of it in the optically less dense medium is 90o Total internal reflectionReflection of light rays within the optically denser medium when the angle of incidence in the optically denser medium is more than the critical angleN.A.Illustrative diagramsRefractionCritical angleTotal internal reflection117856043127000114109515356501178560370500139689963660300176392510687050082558108950015121034296460017526001588550011811246500800-127069469000i represents the angle of incidence which is less than critical angler represents the angle of refraction which is within the optically less dense medium and is less than 90o i represents the angle of incidence which is equal to critical angler represents the angle of refraction which is along the boundary of the 2 mediums and is equal to 90oi represents the angle of incidence which is more than critical angler represents the angle of reflection which is within the optically denser medium and is equal to i(g) identify the main ideas in total internal reflection and apply them to the use of optical fibres in telecommunication and state the advantages of their useMain ideas in total internal reflectionLight ray has to travel from denser medium towards the less dense mediumAngle of incidence of light ray is more than critical angleThe light ray will reflect internally by the laws of reflection within the denser mediumOptical fibres in telecommunicationsAdvantagesDiagramLight pulses carry telecommunications data at a faster rateLess data loss compared to use of copper wiresOptical fibres are generally cheaper and lighter than copper wires (h) describe the action of a thin lens (both converging and diverging) on a beam of lightDifferencesConverging lensDiverging lensLens typeConvex lensConcave lensLight rays940435-698500927735786130002165351276350018097589471500Ray diagram776605693420principal focus00principal focus763905-171450optical center00optical center1462405534670006940553429000Descriptionof lens actionThe lens is curved,thus the angles of incidence of parallel rays of light differ,causing the rays to change direction differently after passing through the lensThe lens is curved,thus the angles of incidence of parallel rays of light differ,causing the rays to change direction differently after passing through the lensThe front of the lens facing the incident light rays curve outwards The light rays converge at a common focal pointThe front of the lens facing the incident light rays curve inwards The light rays diverge from one another(i) define the term focal length for a converging lensTermDefinitionDiagramFocal length of converging lensDistance between the optical center and the principal focus, where parallel rays of light converge after passing through the lens12343025321300048173550680000474345-38100 focal length(j) draw ray diagrams to illustrate the formation of real and virtual images of an object by a thin converging lens#Object locationImage locationImage propertiesAcroynmUses1 Diminished, inverted, realDIRTelescope2 Diminished, inverted, realDIRCameraEye3 Same size, inverted, realSIRPhotocopier4 Magnified, inverted, realMIRProjector5 Magnified, upright, virtualMUVSpotlight6 Magnified, upright, virtualMUVMagnifying glassSpectaclesImage formation based on object location#12ObjectlocationRaydiagram#34ObjectlocationRaydiagram#56ObjectlocationRaydiagram14. Electromagnetic SpectrumContentProperties of electromagnetic wavesApplications of electromagnetic wavesEffects of electromagnetic waves on cells and tissueLearning OutcomesCandidates should be able to:(a) state that all electromagnetic waves are transverse waves that travel with the same speed in vacuum and state the magnitude of this speed#PointProperty of electromagnetic waves (EM waves)1TypeTransverse wavesElectric and magnetic fields oscillate 90o to each other2LawsThey obey the laws of reflection and refraction3Electric chargeNo electric charge is carried through EM waves4MediumNo medium is required and the wave can travel through vacuum5FrequencyRemains the same all the time6WavelengthDecreases from optically less dense to denser medium7Velocity3 x 108 ms-1 in vacuum, slows down in matterDecreases from optically less dense to denser medium(b) describe the main components of the electromagnetic spectrum (c) state examples of the use of the following components: (i) radiowaves (e.g. radio and television communication) (ii) microwaves (e.g. microwave oven and satellite television) (iii) infra-red (e.g. infra-red remote controllers and intruder alarms) (iv) light (e.g. optical fibres for medical uses and telecommunications) (v) ultra-violet (e.g. sunbeds and sterilisation) (vi) X-rays (e.g. radiological and engineering applications) (vii) gamma rays (e.g. medical treatment)ComponentFrequencyApplicationsDescriptionRadio waves1×10^8HzRadio and television communicationsAble to go around obstructions (due to longer wavelengths)Microwaves1×10^10HzMicrowave ovenWater molecules vibrate millions of times a second to produce heat from frictionSatellite televisionCan penetrate haze, light rain, snow, clouds and smoke with proper alignmentInfra-red1×10^12HzRemote controllersIntruder alarmsAlarm rings when it receives infra-red radiation an intruding human gives outLight(Red)5×10^14HzMedical optical fibres(Violet)TelecommunicationsUltra-violet3×10^16HzSunbedsArtificial tanning (shorter frequency UVA)SterilisationGermicidal lamps (longer frequency UVB/C)X-rays3×10^18HzDiagnose fracturesAirport scannersCan penetrate through all materials other than lead, thus may be applied using X-ray imageryGamma rays3×10^20HzCancer treatmentKill cancer cells in cancerous tumours (high energy waves)Changes in the EM spectrum from radio to gamma wavesFrequencyWavelengthIncreases from radio waves to gamma raysDecreases from radio waves to gamma rays(d) describe the effects of absorbing electromagnetic waves, e.g. heating, ionisation and damage to living cells and tissueEffects of absorbing electromagnetic wavesInfraredHigh energy EM wavesX-raysHuman skin absorbs infrared waves from BBQ pits Human bodies will receive the radiation and be heated to feel warmEM waves of frequencies higher than light have high energy causing ionisationIonisation of living matter in human bodies damages chromosomes, living cells and tissuesOverexposure leads to premature ageing and lifespan shorteningOverexposure of developing fetus to X-ray imagery can cause abnormal cell division A deformed baby and leukemia may result15. SoundContentSound wavesSpeed of soundEchoUltrasoundLearning OutcomesCandidates should be able to:(a) describe the production of sound by vibrating sources (b) describe the longitudinal nature of sound waves in terms of the processes of compression and rarefactionProduction of sound in airDescription of sound wavesA vibrating source causes particles in air to be displaced, moving away and from the source continuously Air particles oscillate left and right to produce compressions at high air pressure and rarefactions at low air pressure A longitudinal sound wave is produced(c) explain that a medium is required in order to transmit sound waves and the speed of sound differs in air, liquids and solidsConditions for transmission of sound wavesApproximate speeds of soundA vibrating source must be presentThe source must be placed in a mediumEnergy transmitted by sound waves depends on its frequency and amplitudeSpeed of sound increases from gas to solidIn gasesAir330 m s-1In liquidsWater1500 m s-1In solidsIron5000 m s-1Steel6000 m s-1(d) describe a direct method for the determination of the speed of sound in air and make the necessary calculationExperiment to determine speed of sound in airMethodCalculationReliabilityObservers A and B are positioned at a far distance apart, S, to minimise human reaction errorObserver A fires a pistol and Observer B starts the stopwatch on seeing the flash of the pistolHe stops the stopwatch when he hears the soundThe time interval between the two actions, T, is recordedSpeed of sound is calculated by the following formula: For better accuracy, the experiment is repeated and the average speed of sound is calculatedThe experiment is further repeated by interchanging the positions of Observers A and B to minimise the effects of wind(e) relate loudness of a sound wave to its amplitude and pitch to its frequencyCauseFrequency increasesAmplitude increasesEffects onPitchIncreasesRemains the sameLoudnessRemains the sameIncreases(f) describe how the reflection of sound may produce an echo, and how this may be used for measuring distancesExperiment to measure distances using echoesTheoryMethodCalculationReliabilitySound waves follow the laws of reflectlonThe harder and larger the surface is, the stronger the echoWhen sound waves are reflected after striking objects, the reflected sound, an echo, is producedWhen a source emits a sound and then receives an echo, the sound must have travelled a distance of 2D, where D is the distance between the source and the reflected surfaceThe time interval between emission and receiving of the sound is recorded as TThe speed of sound in the medium is labelled as VDistance from source and reflected surface is calculated by the following formula: For better accuracy, the experiment is repeated and the average distance is calculatedExample of measuring distances using echoes (depth of seabed)DiagramCalculation (g) define ultrasound and describe one use of ultrasound, e.g. quality control and pre-natal scanningTermDefinitionUsesDescriptionMechanismUltrasoundSound with waves above 20 kHz frequency, which is above the upper limit of the human hearing range(Humans can only hear sound of frequencies between 20 Hz to 20 kHz)Quality controlManufactures of various concrete types check for cracks or cavities in concrete slabs with ultrasoundto ensure that their concrete are of the highest qualityUltrasound is released from an emitter at one end of the concrete slab anda sensor is positioned at the other end to detect the ultrasoundIf the speed of sound recorded is lower than actual, this means parts of the concrete contain airPre-natal scanningUltrasound can be used to obtain images of inside a body,thus is used to examine development of a foetus in a pregnant womanUltrasound pulses are sent into the body using a trasmitterEchoes reflected from any surface within the body are receivedThe time interval is noted to determine the depth of the reflecting surface within the bodySECTION V: ELECTRICITY AND MAGNETISMOverviewFor a long time, electricity and magnetism were seen as independent phenomena. Hans Christian Oersted, in 1802, discovered that a current carrying conductor deflected a compass needle. This discovery was overlooked by the scientific community until 18 years later. It may be a chance discovery, but it takes an observant scientist to notice. The exact relationship between an electric current and the magnetic field it produced was deduced mainly through the work of Andre Marie Ampere. However, the major discoveries in electromagnetism were made by two of the greatest names in physics, Michael Faraday and James Clerk Maxwell.The section begins with a discussion of electric charges that are static, i.e. not moving. Next, we study the phenomena associated with moving charges and the concepts of current, voltage and resistance. We also study how these concepts are applied to simple circuits and household electricity. Thereafter, we study the interaction of magnetic fields to pave the way for the study of the interrelationship between electricity and magnetism. The phenomenon in which a current interacts with a magnetic field is studied in electromagnetism, while the phenomenon in which a current or electromotive force is induced in a moving conductor within a magnetic field is studied in electromagnetic induction.Extracted from CHEMISTRY GCE ORDINARY LEVEL (2014) Syllabus Document16. Static ElectricityContentLaws of electrostaticsPrinciples of electrostaticsElectric fieldApplications of electrostaticsLearning OutcomesCandidates should be able to:(a) state that there are positive and negative charges and that charge is measured in coulombsChargeTypes MeasurementPositiveNegativeCharge is measured in coulombs (C)For example, one negative electron has a charge of 1.6 x 10-19 C(b) state that unlike charges attract and like charges repelInteraction of chargesCombination of chargesInteractionUnlike charges Positive-negativeAttractLike chargesPositive-positiveRepelNegative-negative(c) describe an electric field as a region in which an electric charge experiences a force (d) draw the electric field of an isolated point charge and recall that the direction of the field lines gives the direction of the force acting on a positive test chargeTermDefinitionElectric field Region in which an electric charge experiences a forceElectric field linesGives direction of the electric field (i.e. direction of the force on a small positive charge)Electric field of an isolated point chargePositive chargeNegative chargeDiagramField linesFrom chargeTowards charge(e) draw the electric field pattern between two isolated point chargesElectric field of an isolated point chargePositive-negativePositive-positiveNegative-negative5575305543550075565066738500Opposite charges attract,hence the two charges are linked by field lines Like charges repel,hence no field lines connect the two chargesElectric field of parallel charged plates(f) show understanding that electrostatic charging by rubbing involves a transfer of electronsExperimental method of rubbing (to show electrostatic charging between 2 uncharged materials)ActionResultRub two different materials against each otherSome negatively charged electrons are transferred from one material to the otherAn object becomes negatively charged if it gains electrons and positively charged if it loses electronsEase of loss of electrons between objectsEase of loss of electrons generally decreases down the following list:Electron lossObject typeExamplesElectron transferEasiestTransparent objectGlass, PerspexSmooth, high surface area objectSilk, Fur, Hair, WoolHardestOpaque objectEbonite, Rubber, Polyethene(g) describe experiments to show electrostatic charging by inductionExperimental method of induction (to show electrostatic charging of a single metal conductor)#ActionResultDiagram1To negatively charge a neutral conductor, bring a positively charged rod near itLike charges repel and unlike charges attract each otherThus the positively charged rod leaves an excess of negative charges at the side of conductor nearest to the rod and positive charges at the other side by induction2Earth the side of the conductor with the positive chargesElectrons flow from Earth to the conductor to neutralise the positive charges3Remove the Earth, then the rodElectron migration causes the rod to be completely negatively chargedExperimental method of induction (to show electrostatic charging of 2 metal spheres)#ActionResult1Let the two conductors (metal spheres on insulating stands) touch each otherBring a negatively charged rod near the conductor on the leftThe negatively charged rod induces the charges in the two conductors,repelling the negative charges to the furthest end of the conductor on the right,leaving excess positive charges at the end of conductor on the left nearest to the rod2Separate the two conductors far from each otherRemove the rodThe conductor on the left will be positively chargedwhile the other on the right will be negatively charged(h) describe examples where electrostatic charging may be a potential hazardPotential hazards of electrostatic chargingLightningElectrostatic dischargeFriction between water molecules in thunderclouds and air molecules in the air cause the thunderclouds to be chargedAir is ionised when the charge on the thunderclouds becomes large enoughThe ionised air provides a conducting path for the huge quantity of electric charge on the thunderclouds to the nearest object or sharpest object on the ground via lightning strikes during a sudden dischargeElectrostatic charging is thus a potential hazard for people when they are out in an open field or under a tall tree during a thunderstorm, especially in the absence of a lightning conductorFriction between objects may cause excessive charges to build up in them:Friction between tyres of a truck and the road can result in sudden dischargeSparks and subsequent ignition of flammable items on the truck may occur when this happensFriction between electronic equipment (e.g. computer boards, hard drives) and other objects can result in electrostatic discharges over timeThese electronic equipment may be damaged as this happens(i) describe the use of electrostatic charging in a photocopier, and apply the use of electrostatic charging to new situationsComponents of the photocopierPhotoreceptor drumLaser assemblyTonerFuserMetal drum rollerCoated with a photoconductive layerLaserMovable mirrorLensFine negatively charged powderHeat sourceElectrostatic charging in a photocopier#ActionResultDiagram1A photoreceptor drum is rotated near a highly positively charged corona wireThe photoreceptor drum becomes positively charged2The laser beam is cast over a page of the original document through a lens onto the photoreceptor drumAreas of photoconductive layer on the drum surface that are exposed to the laser is dischargedNegatively charged toner is then attracted to the remaining positively charged areas3Toner on the drum is transferred to the paperPaper is heated by the fuserToner power melts onto the paper surface, affixing itself permanently on the surfaceNote: A laser printer operates differently from a photocopier, although both rely on electrostatic charging17. Current of ElectricityContentConventional current and electron flowElectromotive forcePotential differenceResistanceLearning OutcomesCandidates should be able to:(a) state that current is a rate of flow of charge and that it is measured in amperesTermDefinitionMeasurementFormulaSI unitsCurrentA measure of the rate of flow of electric charge through a cross section of a conductorAmmeterConnected in series IQtACs(b) distinguish between conventional current and electron flowConventional current flowElectron flowCombined flow of chargesFlow of positive charges from a positively charged end to a negatively charged end (i.e. current)Flow of electrons from a negatively charged end to a positively charged end(c) recall and apply the relationship charge = current × time to new situations or to solve related problemsTermDefinitionFormulaSI unitsChargeWhen an object is charged, it is electrifiedEquals to the product of current and time QItCAs(d) define electromotive force (e.m.f.) as the work done by a source in driving unit charge around a complete circuitTermDefinitionMeasurementFormulaSI unitsElectro-motive forceWork done by an electrical source in driving a unit charge round a complete circuitVoltmeterConnected in parallel across the positive and negative ends of the electrical source WQVJC(e) calculate the total e.m.f. where several sources are arranged in seriesExample of circuit of 3 dry cells as sourcesDiagramReadings recordedTotal e.m.f.VoltmeterDry cell e.m.f. 11.5 V21.5 V33 V(f) state that the e.m.f. of a source and the potential difference (p.d.) across a circuit component is measured in volts (g) define the p.d. across a component in a circuit as the work done to drive unit charge through the componentTermDefinitionMeasurementFormulaSI unitsPotential differenceAmount of energy converted to other forms of energy when one coulomb of positive charge passes between 2 reference pointsVoltmeterConnected in parallel across the 2 points QtACs(h) state the definition that resistance = p.d. / current (i) apply the relationship R = V/I to new situations or to solve related problemsTermDefinitionFactorsFormula 1SI unitsResistanceRatio of the potential difference across a component to the current flowing through itLengthCross sectional areaType of material RVIΩ or ohmVA(j) describe an experiment to determine the resistance of a metallic conductor using a voltmeter and an ammeter, and make the necessary calculationsExperiment to determine resistance of a metallic conductorMethodCalculationConnect a dry cell, rheostat and ammeter in series to the metallic conductorIn the same circuit, connect a voltmeter in parallel to the metallic conductorVary the resistance of the rheostat and and note down values of V (reading of voltmeter) and I (reading of ammeter) for at least 5 sets of readingsBy Ohm’s law, resistance R will be equivalent to the voltage divided by current Hence, plot a graph of V against I to find the gradient of the graph, R(k) recall and apply the formulae for the effective resistance of a number of resistors in series and in parallel to new situations or to solve related problemsDifferencesResistors in seriesResistors in parallelCircuit diagramwhere R1 and R2 arethe resistances of theresistors respectivelywhere R1 and R2 arethe resistances of theresistors respectivelyFormula foreffective resistancefor the circuit above Nature ofeffective resistance General formula foreffective resistance (l) recall and apply the relationship of the proportionality between resistance and the length and cross-sectional area of a wire to new situations or to solve related problemsDifferencesResistance of materialResistivity of materialMain formula UnitΩΩ mNatureResistance increases as length increasesResistance increases as cross-sectional area decreasesIndependent of length & cross-sectional areaTermFormula 2SI unitsRelationshipsResistance RlA ΩΩ mmm2(m) state Ohm’s LawLawDefinitionRelationshipOhm’s LawCurrent passing through a metallic conductor is directly proportional to the potential difference across its ends, provided the physical conditions are constant (n) describe the effect of temperature increase on the resistance of a metallic conductorEffect of temperature increase on resistanceExplanationResistance of metallic conductor increasesParticles in metallic conductor gain kinetic energy and vibrate fasterThis causes electrons moving through the conductor to slow down(o) sketch and interpret the I/V characteristic graphs for a metallic conductor at constant temperature, for a filament lamp and for a semiconductor diodeDifferencesOhmic conductorsNon-ohmic conductors (examples)Filament lampSemiconductor diodePurposeN.A.Provides light indoors and at nightAllows current to flow in only one direction (i.e. forward direction) through the circuit I/V sketchV/I sketch(invert the I/V sketch along the line V=I)InterpretationOhmic conductors follow Ohm’s lawThe filament lamp is a non-ohmic conductorThe semiconductor diode is another non-ohmic conductorGradient V/I is constant since I is directly proportional to VGradient V/I increases as V increases across the lampThis is because as p.d. increases, the current increases less than proportionatelyThis indicates that resistance of the lamp increases as p.d. increasesGradient V/I decreases as V increases from zero This is because as p.d. increases, the current increases more than proportionatelyThis indicates that resistance decreases when p.d. in the forward direction increases, allowing a relatively large current, I, to flow throughGradient V/I is very large as V increases to zero This indicates that resistance is very high when p.d. in the reverse direction increasesAlmost no current flows in this reverse direction18. D.C. CircuitsContentCurrent and potential difference in circuitsSeries and parallel circuitsPotential divider circuitThermistor and light-dependent resistorLearning OutcomesCandidates should be able to:(a) draw circuit diagrams with power sources (cell, battery, d.c. supply or a.c. supply), switches, lamps, resistors (fixed and variable), variable potential divider (potentiometer), fuses, ammeters and voltmeters, bells, light-dependent resistors, thermistors and light-emitting diodesSymbols of power sourcesSymbols of common componentsCellBatteryD.C supplyA.C. supplyLampBell SwitchFuseSymbols of resistors and diodesFixed resistorVariable resistorThermistorLight-dependent resistorLight-emitting diodeSymbols of measurement devicesSymbols of other devicesAmmeterVoltmeterPotentiometerCircuit diagram exampleExperimental setupCircuit diagram(b) state that the current at every point in a series circuit is the same and apply the principle to new situations or to solve related problems (c) state that the sum of the potential differences in a series circuit is equal to the potential difference across the whole circuit and apply the principle to new situations or to solve related problems (d) state that the current from the source is the sum of the currents in the separate branches of a parallel circuit and apply the principle to new situations or to solve related problems (e) state that the potential difference across the separate branches of a parallel circuit is the same and apply the principle to new situations or to solve related problemsCircuitCurrent in circuitPotential difference across whole circuitSeriesSame at every pointSum of potential differences in circuitParallelSum of currents in the separate branchesSame as across the separate branches(f) recall and apply the relevant relationships, including R = V/I and those for current, potential differences and resistors in series and in parallel circuits, in calculations involving a whole circuitTermFormulaSI unitsRemarksResistance RVIWhen the circuit has resistors in both the series and parallel arrangement, calculate effective resistance of the ones arranged in parallel firstΩ or ohmVA(g) describe the action of a variable potential divider (potentiometer)Purpose of potentiometerAction of potentiometerA potentiometer is able to divide the supply voltage in any ratio that is required by varying resistance and using the formula The potentiometer is made of a conducting slider in contact with a resistor with fixed cross-sectional areaBy sliding the slider along the resistor, the length of the resistance material that the current of the circuit has to flow through can be variedSince , resistance of the circuit increases when the length increasesAs , potential difference across the circuit can thus be adjusted between zero and the maximum supply voltage(h) describe the action of thermistors and light-dependent resistors and explain their use as input transducers in potential dividers (i) solve simple circuit problems involving thermistors and light-dependent resistorsInput tranducersTransducers that convert non-electrical energy to electrical energyDifferencesThermistorLight-dependent resistorDeviceA device whose resistance decreases when temperature increasesA device whose resistance decreases as the amount of light shining on it increasesApplicationsTemperature controlTemperature measurement in fire alarmsUnder bright lighting, the LDR would have very low resistance, and vice versa19. Practical ElectricityContentElectric power and energyDangers of electricitySafe use of electricity in the homeLearning OutcomesCandidates should be able to:(a) describe the use of the heating effect of electricity in appliances such as electric kettles, ovens and heatersUse of electricityDescription of useHeating effectUsed in heating appliances like electric kettles, ovens and heatersHeating elements in heating appliances musthave high resistivity (high resistance per unit length of material of constant cross-sectional area) and must be able to withstand high temperaturesWhen current passes through these elements (e.g. nichrome) in heating appliances when, much heat is generatedBy varying current passing through, heat produced by Joule heating can be effectively controlled(b) recall and apply the relationships P = VI and E = VIt to new situations or to solve related problemsTermFormulaSI unitsDerivation of formulaeElectrical energy EVIt is derived from: JVAsElectrical power PVIWVA(c) calculate the cost of using electrical appliances where the energy unit is the kW hTermFormulaSI unitsElectrical energy EPtkWhkWhCost of using electrical appliances CostEnergyRate?kWh? per kWh(d) compare the use of non-renewable and renewable energy sources such as fossil fuels, nuclear energy, solar energy, wind energy and hydroelectric generation to generate electricity in terms of energy conversion efficiency, cost per kW h produced and environmental impactEnergysourceRenewabilityEnergy conversion SourceEfficiencyReasonsFossil fuels Non-renewableChemical potential energy30-40%Good distribution system of electricity from fossil fuels in many countries Nuclearenergy Non-renewableNuclear energy30-40%Only a small amount of uranium is needed to generate a large amount of energySolar energy RenewableLight energy10-20%Efficiency is high only when there is daylight and minimal cloud coverWind energyRenewableKinetic energy30-40%Wind direction and speed variesHydroelectricgenerationRenewableGravitational potential energy90%Water flowis concentratedcan be easily controlledNon-renewable energy sourcesEnergy sourceCost per kWh producedEnvironmental impactFossil fuels High costs due to lower availability of fossilshigher energy demandGases produced as a result of the combustion of fossil fuels are usually pollutive (e.g. may combine with rain to form acid rain)Nuclear energy Radioactivity, when leaked, is very expensive to clean up Radioactivity, when leaked, is difficult and expensive to clean up Threat to safety as it can cause mutations to humansNon-renewable energy sourcesEnergy sourceCost per kWh producedEnvironmental impactCons ProsCons ProsSolar energy High costs involved in manufacturing Cost of fuel (i.e. sunlight) is freeClean energyLarge areas must be cleared to make space for the solar panelsWind energyFalling costs due to technological improvementsCost of fuel (i.e. wind) is freeClean energySpinning turbines cause noise pollutionHydroelectricgenerationHigh costs involved in constructing the dam and power plant togethermaintanence in clearing of slit blocking water flow behind the damN.A.Clean energyDams built may disrupt ecosystems(e) state the hazards of using electricity in the following situations: (i) damaged insulation (ii) overheating of cables (iii) damp conditionsHazards of using electricityDamaged insulationOverheating cablesDamp conditionsIf one touches the exposed live wire, electrons flow through the body to EarthMay cause severe electric shock, injury and deathMany electrical appliances used concurrentlyTotal power drawn from the mains supply may be very largeWires not thick enough will produce high resistance producing more heat Cable becomes overheated to result in a fireWater is a good conductor of electricity Provides conducting path for large current to flowSince the human body has very low resistanceHuman body is electrocuted when current of more than 50 mA flows through(f) explain the use of fuses and circuit breakers in electrical circuits and of fuse ratingsSafety devicesUse of fusesUse of circuit breakersInternal wire melts when excessive current flows throughThe fuse rating on a fuse indicates the maximum current that can flow through it before the fuse starts to meltProtects electrical appliances from damageEnsures safety of the userSwitches off electrical supply in a circuit when there is overflow of currentThe miniature circuit breaker trips when there is a fault in the circuitThe Earth leakage circuit breaker switches off all circuits in the house when there is an Earth leakage of more than 25 mA from the live to earth wireMust be replacedMay be reset after problem is resolved(g) explain the need for earthing metal cases and for double insulationSafety precautionsNeed for earthing metal casesNeed for double insulationIn case the live wire comes into contact with the metal casing by accident, someone who touches the casing will be electrocutedTo ensure the safety of the user, the metal casing is earthedAn earth wire is connected to casing to conduct current away to the earth directly instead of going through the human bodyAppliances with plugs of two pins have no earth wireDouble insulation insulates electric cable from internal components and insulates the internal components from external casing of these appliances(h) state the meaning of the terms live, neutral and earthTermMeaningLiveWire which delivers electrical energy to appliance at high voltage, allowing the appliance to functionNeutralWire kept at zero volts which forms a current flow path back to the supply to complete the circuitEarthLow resistance wire which connects the metal casing of an equipment to Earth, earthing the appliance continuously to ensure electrical safety of the user in case the metal casing becomes live(i) describe the wiring in a mains plugWiring in a mains plugDescriptionThe cable is made up of 3 wires: the live, netural and earth wiresWireColourExplanationLiveBrownWired into the pin on the rightA fuse is placed between the live terminal and the live pin in the circuitThe fuse breaks the circuit if too much current flowsNeutralBlueWired into the pin on the leftEarthGreen and yellow stripesWired into the pin on the top(j) explain why switches, fuses, and circuit breakers are wired into the live conductorWiring of safety devicesExplanationSwitches, fuses and circuit breakers are wired into the live conductorSwitches, fuses and circuit breakers work by breaking an electric circuitBy being wired into live conductor, it will be able to prevent current flow from flowing into the conductor at allDamage to the conductor is prevented20. MagnetismContentLaws of magnetismMagnetic properties of matterMagnetic fieldLearning OutcomesCandidates should be able to:(a) state the properties of magnets#Properties of magnetsAspectDescription of property1Magnetic polesHave magnetic poles, where the magnetic effects are strongest2Alignment when suspended freelyAlign themselves to the north and south poles of the Earth when suspended freely3Interaction with magnetic materialsAttract magnetic materials, which are iron, steel, nickel and cobalt4Interaction with other magnets Repel from another magnet with like poles and attracts magnets with unlike poles5IdentificationCan only be identified by repulsion(b) describe induced magnetismMeaning of induced magnetismMechanism of induced magnetismMagnetic materials are magnetised temporarily when near or in contact with a permanent magnet Magnetic field from the magnetic material aligns with the domains of the permanent magnet(c) describe electrical methods of magnetisation and demagnetisationElectrical magnetisationElectrical demagnetisationMagnetic object placed in a solenoid (a cylindrical coil of insulated copper wires carrying currents)Strong magnetic field produced when direct electric current, D.C., flows through the solenoidThe magnetic field produced will magnetise the magnetic objectField is determined by right-hand grip rule:Magnet is inserted into a solenoid and an alternating current, A.C., flows through itWhen the magnet is withdrawn slowly from the coil, the magnet is constantly being magnetised in opposite directions by the alternating currentThe domains in the magnet will be arranged different directions, cancelling their magnetic effectMagnetic field around the solenoid causes the magnet to lose its magnetismProperties of magnetised objectsProperties of demagnetised objectsHave properties of a magnetMagnetic domains point in the same directionDo not have any properties of a magnetMagnetic domains point in random directionsNo resultant magnetic effect present(d) draw the magnetic field pattern around a bar magnet and between the poles of two bar magnets (e) describe the plotting of magnetic field lines with a compassExamples of magnetic field patternsMethod to draw magnetic field patternThe magnetic field pattern of a single permanent magnet is shown on the rightField lines travel from N to S outside the magnetField lines travel from S to N through the magnetPlace the bar magnet at centre of piece of paper so that its North pole faces north and its South pole faces southPlace a compass near one pole of the magnet and mark with dots the positions of the North and South ends of the compass needle, labeling them Y and X respectivelyMove the compass such that the south end of the compass needle is exactly over YMark the new posltlon of the north end with a third dot labeled ZRepeat the above until the compass reaches the other pole of the bar magnetJoin the series of dots with a curve and this will give a field line of the magnetic fieldRepeat for more field lines and indicate the direction of the lines(f) distinguish between the properties and uses of temporary magnets (e.g. iron) and permanent magnets (e.g. steel)DifferencesTemporary magnetsPermanent magnetsExampleMagnetised ironMagnetised steelNatureSoft magnetic materialHard magnetic materialEase of magnetisationEasily magnetisedHard to magnetiseRetainment of magnetismDo not easily retain magnetismEasily retains magnetismUsesElectromagnetTransformer coreShieldingMagnetic door catchMoving-coil ammeterMoving-coil loudspeaker21. ElectromagnetismContentMagnetic effect of a currentApplications of the magnetic effect of a currentForce on a current-carrying conductorThe d.c. motorLearning OutcomesCandidates should be able to:(a) draw the pattern of the magnetic field due to currents in straight wires and in solenoids and state the effect on the magnetic field of changing the magnitude and/or direction of the currentScenarioPatterns of magnetic field due to currentCurrent in solenoidsCaseClockwiseAnti-clockwiseFront-view1407160-203200057658068135500564515-254000065532064135000665480-4572000The arrows represent the direction of currentA cross indicates magnetic field lines travelling inwards into the plane (away from you)The arrows represent the direction of currentA dot indicates magnetic field lines travelling outwards from the plane (towards from you)Representations of arrows and cross/dot can be interchanged (i.e. cross/dot can represent direction of current, arrows represent magnetic field)Representations of arrows and cross/dot can be interchanged (i.e. cross/dot can represent direction of current, arrows represent magnetic field)Side-viewCurrents in straight wiresCaseCurrent in the same directionCurrent in opposite directions Magnetic fieldIllustrationRemarksThe most common rule used here is the right hand grip rule [which has been illustrated in learning outcome 20(c)](b) describe the application of the magnetic effect of a current in a circuit breakerMagnetic effect of currentWhen current is increased to a high level, the solenoid of circuit breaker gains magnetism and becomes a strong electromagnetStronger magnetic fields produce a force that enables the solenoid to attract iron armature connected in the circuit, breaking the circuitWhen current is within the limitWhen there is a short circuit or overloadThe solenoid magnetic field is not strong enough to attract the soft iron latchThe interrupt point remains closed and current flows normally through the circuitA sudden surge of current is presentSolenoid gains magnetism and becomes a strong electromagnet due to larger currentIt is able to attract the soft iron latch and release the springThe safety bar is pushed outwardThe interrupt point opens and current is cut off(c) describe experiments to show the force on a current-carrying conductor, and on a beam of charged particles, in a magnetic field, including the effect of reversing (i) the current (ii) the direction of the fieldCurrent-carrying conductor in magnetic fieldCurrent-carrying conductorMagnetic field from magnetsExplanationIn this case, current that flows outwards in a straight line instead of in a solenoid will cause magnetic field lines to travel anti-clockwiseField lines at the top of the wire flow in the same direction as the magnetic field from the magnetsOn the other hand, field lines at the bottom of the wire flow in the opposite direction as the magnetic field from the magnetsCombined diagramExplanationExperimental setupAs a result, when the conductor is placed in the magnetic field from the magnets, the magnetic field produced above the wire will be much stronger than the magnetic field produced below the wireThe strong resultant magnetic field at the top causes a force to push the conductor downwardsRemarksThe most common rule used here is Fleming’s left-hand rule [which will be illustrated in the next learning outcome]This rule is used only when current from a source causes a force to be producedBeam of charged particles in magnetic fieldCasePositive chargeNegative charge Force directionA cross indicates magnetic field lines travelling inwards into the plane (away from you)RemarksThe most common rule used here is Fleming’s left-hand rule [which will be illustrated in the next learning outcome]This rule is used only when current from a source causes a force to be produced(d) deduce the relative directions of force, field and current when any two of these quantities are at right angles to each other using Fleming’s left-hand ruleFleming’s left-hand ruleFunctionIllustration using current-carrying conductorLegendThe relative directions of force, field and currents for both a current-carrying conductor and a beam of charged particles illustrated above can be found using your left hand by Fleming’s left-hand ruleThis rule is used only when current from a source causes a force to be produced1593215760730I00I1096010259715F00F1600200456565B00BFingerDirectionSymbol1Force F2Magnetic fieldB3CurrentI(e) describe the field patterns between currents in parallel conductors and relate these to the forces which exist between the conductors (excluding the Earth’s field)DifferencesCurrents in parallel conductorsCaseCurrent in the same directionCurrent in opposite directions Magnetic fieldRespective993140-400050015176566294000186690-4254500671195-33020001034415-2095500232410-20955001924056356350034925065659000CombinedIllustrationExplanationThe magnetic field lines in between the conductors (both currents travelling inwards) are in opposite directions, cancelling out each otherThis causes the magnetic field to be stronger in all other areas, pushing the conductors towards each otherThe magnetic field lines in between the conductors (currents in opposite directions) are in the same direction, which intensifies the magnetic field present thereSince the magnetic field is now stronger in between the conductors than all the other areas, the conductors are pushed away from each other(f) explain how a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing (i) the number of turns on the coil (ii) the current Turning effect due to current-carrying coil in a magnetic fieldCaseDue to pivot120015013462000131000519621500Due to axisDiagram200025099695000150685512179300015652751017270001544955866775001360170998855001499870367665001254125110299500110236084836000ExplanationAs current through the thick, stiff copper wire and magnetic field are perpendicular to each other,by Fleming’s left hand rule,a force is produced that pushes the wire away from the powerful permanent magnetSince the bent stiff copper or brass wire acts as a pivot,a perpendicular distance between the pivot and the force is present,thus a clockwise turning effect is also produced 1272540-51074As current through the coil and magnetic field are perpendicular to each other at both sides,by Fleming’s left hand rule,a force is producedThe coil at the side nearer to the N pole is pushed forward as current travels upwardswhereas the coil at the side nearer to the S pole is pushed backward as current as travels downwardsThis produces an anti-clockwise turning effect about a central axis (dotted lines)Increasing force of the turning effectBy increasing number of turns of coilBy increasing currentEach loop of wires produces its own magnetic fieldSince the magnetic field strength is the sum of the field lines,more lines will produce a stronger magnetic field and hence greater forceA larger current will produce a greater concentration of field linesA strong field will lead to a larger force(g) discuss how this turning effect is used in the action of an electric motorDifferencesUses of electrically produced turning effectsD.C. motorsA.C. motorsExamplesToy carsDVDsHard disksElectric fansHair dryersWashing machinesReasonRotation in a fixed direction is requiredAlternating rotation in the clockwise and anticlockwise directions is required(h) describe the action of a split-ring commutator in a two-pole, single-coil motor and the effect of winding the coil on to a soft-iron cylinderSplit-ring commutatorDiagramDescriptionConstant magnetic field by two permanent magnets interacts with the magnetic field in the U-shaped coil due to the direct currentBased on Fleming’s left hand rule, the wires at each side of the coil experience an equal but opposite forceThe turning effect created by the two forces causes the coil to rotate continuously in the same directionSplit-ring commutatorMain componentsFunction of componentsTwo permanent magnetsN and S poles of both magnets face each otherProvides the magnetic field (B)D.C. circuitProvides the direct current flow (I)Pair of carbon brushesMaintains continuous contact between the stationary external D.C. circuit and the split-ring commutator, which is linked to the rotating coilEnsures that the circuit is never broken during rotationSplit-ring commutatorPlaced between the coil and carbon brushesReverses direction of current in the coil every half a turn by the coilEnsures the coil rotates in the same (clockwise) direction thoroughout (if it is a continuous ring commutator, the coil will rotate in alternate directions instead)Soft-iron cylindrical coreWinding the coil on to a soft-iron cylindrical core concentrates the magnetic field, increasing magnetic field strength22. Electromagnetic InductionContentPrinciples of electromagnetic inductionThe a.c. generatorUse of cathode-ray oscilloscopeThe transformerLearning OutcomesCandidates should be able to:(a) deduce from Faraday’s experiments on electromagnetic induction or other appropriate experiments: (i) that a changing magnetic field can induce an e.m.f. in a circuit (ii) that the direction of the induced e.m.f. opposes the change producing itElectromagnetic inductionLawsFaraday’s lawLenz’s lawDefinitionE.m.f. generated in a conductoris proportional to the rate of change of the magnetic lines of force linking with the circuitDirection of the induced e.m.f. and hence the induced current in a closed circuit is always such as to oppose the change in the applied magnetic fieldPrinciplesChanging magnetic field can induce an e.m.f. in a circuitDirection of the induced e.m.f. opposes the change producing itDescription of principleChanging magnetic field produces a continuously changing magnetic flux linking with the secondary solenoidSince Faraday’s law states e.m.f. generated in a conductoris proportional to the rate of change of the magnetic lines of force linking with the circuit,e.m.f. will be induced, producing a current that will allow power to be transmittedSince Lenz’s law states direction of the induced e.m.f. and hence the induced current in a closed circuit is always such as to oppose the change in the applied magnetic field,the drawing in of a north pole of a magnet into a solenoid (or drawing out of a south pole)will produce a north pole at the end of the solenoid nearest to the magnet as the solenoid will repel the magnet,and vice versaExperiments1079585026500Opposite direction of magnetic fieldOpposite direction of magnetic field71755-3111500(iii) the factors affecting the magnitude of the induced e.m.f.Factors to increase the magnitude of induced e.m.f.Increased number of turns of coilIncreased strength of magnetIncreased speed of movement of magnet or coilAddition of a soft iron coreIncreased number of turns of coilsince more magnetic lines of forceproduce stronger magnetic field and hence greater forceIncreased strength of magnetwill produce a stronger magnetic fieldand hence greater forceIncreased speed of movement of magnet or coil in displacement to each otherwill increase rate of change of magnetic field linesand frequency of the emf against time graphAddition of a soft iron coresince it becomes a magnet within the field linessuch that it increases the concentration of magnetic field linesThe above factors increase the rate of change of magnetic flux linking the circuit and hence emf by Faraday’s law(b) describe a simple form of a.c. generator (rotating coil or rotating magnet) and the use of slip rings (where needed) (c) sketch a graph of voltage output against time for a simple a.c. generatorA.C. generator [read ‘Remarks’ to understand Fleming’s right hand rule first]Diagram of generatorDiagram of electrical loadGraph of induced e.m.f. / timeA.C. voltage from the generator may be received by an electrical load (e.g. light bulb) connected to it11823701390650001184275138938000103695512903200069088012122150068643512103100035115513017500020320013868400010356851287780003479801301115002012951386840001177290119634000836295128651000683895138684000194310120269000527685130048000-8255-45085induced e.m.f. / mV00induced e.m.f. / mVUse of slip ringsDescription of action of A.C. generatorKeeps the electrical load in a fixed position (instead of rotating continuously)Maintains continuous contact with the carbon brushes when the coil is rotatingThis ensures that the alternating current induced in the coil is transferred to the external circuitElectromagnetic device which transforms mechanical energy into electrical energyCoil is rotated (usually with a handle) about an axis between the two opposing poles of a permanent magnetWhen rectangular coil is parallel to the magnetic lines of force, both sides of the coil cuts through the magnetic field lines at the greatest rate, hence induced e.m.f. is maximumThe next time rectangular coil becomes parallel to the magnetic lines of force, current will be reversed and thus induced e.m.f. will be minimumWhen rectangular coil is perpendicular to the magnetic lines of force, it is not cutting through the magnetic field linesThe rate of change of magnetic lines of force at this instance is zero, hence no e.m.f. is inducedRemarksThe most common rule used here is Fleming’s right-hand rule, which is used when the application of a force causes current to be producedThis is as opposed to Fleming’s left-hand rule, which is used only when current from a source causes a force to be produced2613248756920I00I2608803305435B00B3242087309245F00FFactors affecting graph of induced e.m.f. against timeNumber of coilsStrength of magnetSpeed of rotationWhen number of coils doubles,amplitude doubles,frequency doubles andwavelength halvesWhen strength of magnet doubles,only amplitude doublesWhen speed of rotation doubles,only amplitude doubles(d) describe the use of a cathode-ray oscilloscope (c.r.o.) to display waveforms and to measure potential differences and short intervals of time (detailed circuits, structure and operation of the c.r.o. are not required)Cathode-ray oscilloscopeDiagram for understanding onlyMechanism for understanding onlyThe electron gun emits a cathode-ray (i.e. beam of electrons) through thermonic emissionThe electron beam then strikes the flourescent screen, forming a bright spotThe deflection system of X and Y plates controls the position the electrons strike on the fluorescent screenIt does so by varying the voltage across the X and/or Y platesUsesComponent required to functionMeasure potential differencesVoltage to be measured is applied to the Y-plates via the Y-input terminalsDisplay waveforms of potential differencesThe voltage measured is displayed on the fluorescent screenTime-base is switched off to show a fixed voltage or the amplitude of varying voltageTime-base is switched on to check for varying voltage or its frequency and wavelength Measure short time intervalsThe device used to measure short time intervals between occurrences (e.g. microphone, when a sound is received at intervals) transmits the information received into voltageThe voltage display shown represents the short time intervals to be measured(e) interpret c.r.o. displays of waveforms, potential differences and time intervals to solve related problemsTime base / HzY-gain / VSignals being measured will have a wide range of frequenciesAdjusting the time base of input allows us to view the signals to a appropriate range on the screenThe gain determines sensitivity of oscilloscopeAdjusted to measure the voltageExamplesExample 1Example 2Example 3Example 4Input2 V-4 V20 V-20 VY-gain1 V/div2 V/div5 V/div5 V/divGain-input relationshipLine is produced2/1 = 2 div aboveLine is produced -4/2 = 2 div belowNormal sine curve 20/5 = 4 divInverted sine curve 20/5 = 4 divA.C. InputNot A.C. (i.e. 0 Hz)Not A.C. (i.e. 0 Hz)50 Hz25 HzTime base25 Hz25 Hz25 Hz25 HzCycles0/25 = 0 Cycles 0/25 = 0 Cycles50/25 = 2 Cycles50/25 = 1 CycleGraphGraph when time base is turned off(f) describe the structure and principle of operation of a simple iron-cored transformer as used for voltage transformationsSimple iron-cored transformerStructurePrinciplePrimary coil is wound on one side of laminated soft iron core and secondary coil on the other side with different number of turnsThe lamination reduces heat loss due to eddy currents in the soft iron coreApplied alternating voltage at primary coil sets up changing magnetic field passing through soft core to the secondary coilSince Faraday’s law states e.m.f. generated in a conductor is proportional to rate of change of magnetic lines of force linking with the circuit,alternating current at the secondary coil produces a changing magnetic field (based on the turns ratio) which induces e.m.f. by electromagnetic induction(g) recall and apply the equations VP / VS = NP / NS and VPIP = VSIS to new situations or to solve related problems (for an ideal transformer)TermEquationsTurns ratio Power for transformersof 100% efficiency Power for transformersof less than 100% efficiency (h) describe the energy loss in cables and deduce the advantages of high voltage transmissionEnergy loss in cablesAdvantages of high voltage transmissionEnergy loss is due to Joule heating as the product of time, square of current flow and resistance of cablesA decrease of either current flow or resistance of cables or both will decrease energy lossHaving increased voltage will reduce current flow but increase insulation costsHaving thick cables will reduce resistance but increase construction costsAs output power is the product of voltage and current, increased voltage will reduce current flow greatlySince Joule heating is the product of the square of current flow and resistance of cablesPower loss in the form of heat is thus decreased, allowing more power to be transmitted to households-End-NoticeWhile every effort has been made to avoid using copyright material, some copyright material may have been inadvertently used in this set of notes. To these copyright holders, we offer our sincere apologies and hope they will take our liberty in good faith. We would welcome any information which would enable us to contact the copyright owners involved.Under the Creative Commons licence,Editors are free to:Share — copy and redistribute the material in any medium or formatAdapt — remix, transform, and build upon the materialUnder the following terms:Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.NonCommercial — You may not use the material for commercial purposes.ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.Editors should ensure that any material they wish to embed in this set of notes is not copyrighted before proceeding with editing. ................
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