Welcome to A-level Physics
Physics
Reigate Grammar School
Introduction
Welcome to A-level Physics.
The course you are studying is the WJEC (Welsh Joint Education Committee) GCE Physics (3321) course. The course homepage is at 2p64t. Over the next two years you will be expanding your knowledge and extending your practical skills in Physics. The subject matter is broken down into 6 modules:
▪ Motion, Energy & Charge
▪ Waves and Particles
▪ Practical Physics
▪ Oscillations and Fields
▪ Magnetism, Nuclei & Options
▪ Experimental Physics
The details of which can be found on pages 17 to 65.
You will receive 4½ hours of lessons a week and will be expected to do a minimum of 3 hours of work in your own time to reinforce and prepare for the work in lessons; this includes homework. To help you with homework and to understand the material, you have a single text book, Advanced Physics by Adams and Allday. It is substantial book and an excellent source of information and practice questions; do not shy away from using this book.
Throughout the course you will be doing practical work, WJEC is well known for demanding high standards of practical work. The main emphasis of this work will be on the analysis of data. WJEC have produced a guide which you should have with you at all times, it can be found on pages 5 to 16.
WJEC is also known for requiring candidates to use the correct terminology when describing physical processes. Get used to using the correct terminology when in discussion with your teacher or fellow pupil. To help you, WJEC have created a glossary of terms (pages 66 to 73), you must learn the meaning of these terms as well as how to use them. There is also a table to fill in of all the quantities and units that you will use at A level, as well as all the different types of relationship that you will be expected to plot; these can be found on pages 74 to 85.
A level is a stepping stone from GCSE to university. You will therefore have to take much greater responsibility for your learning. We believe that encouraging you to do some independent learning and research is a fundamental part of your education. On page ii is a list of skills that you need to develop over the next two years. We have also identified the topics that naturally lend themselves to independent research; you do not need to wait for a topic to be covered before you read about it. To help guide you to relevant sources and mind-blowing concepts we have compiled a list of books (on page iii) which you should read during the two year course.
At the end of 6th and 7th Forms there are Physics prizes. These are awarded to good scientists that contribute to the science community at RGS and display an appropriate level of excellence.
Finally: your teachers are the best resource that you have; use them.
AGM
July 2008
Independent Research in Physics
As an A-level student you are responsible for your own learning. This responsibility includes reading around the subject material taught in class and going beyond the limits of the syllabus.
We have identified key skills for AS and A2 students. Some of these should be ongoing (like reading journals and books) whilst others might happen once a term (like writing an article).
▪ Keep up with advances in Physics by reading the newspaper, Physics World, Physics Review, New Scientist, Scientific American etc.
▪ Keep up to date with scientific websites (see: ).
▪ Understand how Physics influences the world around us.
▪ Critically assess an article in a scientific journal.
▪ Write your own article for a journal or competition (see youngscientists.co.uk).
▪ Read a popular science novel.
▪ Go to Physics talks at Surrey University or Friday lunch time.
▪ Give your own talk on a Friday lunch time.
▪ Précis information (without plagiarising).
▪ Efficiently present information.
▪ Research a topic efficiently and evaluate the usefulness of resources.
▪ Cite references correctly.
▪ Explore different revision techniques.
▪ Develop investigative skills.
▪ Become an expert in one area of Physics – find your niche!
Some topics that naturally lend themselves to independent research include:
▪ Superconductivity and semiconductors
▪ Wave-particle duality
▪ Optical fibre communications
▪ The uses of X-rays in medicine and how they are created
▪ Lasers and their uses
▪ Particle / high-energy physics
▪ Astrophysics; processes within stars and their gravity
▪ The science of earthquakes
▪ Thermodynamics
▪ Electrical generation and transmission
▪ Radioactivity
We would like you to keep a scrap book to record your independent research.
We will be looking for evidence of development of these key skills in your scrapbook and you will be asked to self assess your progress.
Independent research is key to developing an interest in science and thereby improving UCAS applications for science and science related subjects.
Book List
|[pic] |Annus Mirabilis |
| |by John Gribbin and Mary Gribbin |
|[pic] |A Briefer History of Time |
| |by Stephen Hawking and Leonard Mlodinow |
|[pic] |Cosmos |
| |by Carl Sagan |
|[pic] |The Fabric of the Cosmos |
| |by Brian Greene |
|[pic] |In Search of Schrödinger's Cat |
| |by John Gribbin |
|[pic] |The Never-Ending Days of Being Dead |
| |by Marcus Chown |
|[pic] |QED: The Strange Theory of Light and Matter |
| |by Richard Feynman |
|[pic] |Six Easy Pieces |
| |by Richard Feynman |
|[pic] |The Two Cultures |
| |by C.P. Snow |
|[pic] |The Universe: A Biography |
| |by John Gribbin |
These books are available from the Library.
|[pic] | | |
| |GCE PHYSICS | |
| |TAG FFISEG | |
| |Advanced Level / Safon Uwch | |
Constants, Formulae, and Mathematical Information
A clean copy of this booklet should be issued to candidates for their use during each GCE Physics examination in the new specification. It is not to be used in legacy specification examinations.
Centres are asked to issue this booklet to candidates at the start of the GCE Physics course to enable them to become familiar with its contents and layout.
Fundamental Constants
Avogadro constant NA = 6.02 ( 1023 mol (1
Fundamental electronic charge e = 1(60 ( 10(19 C
Mass of an electron me = 9(11 ( 10(31 kg
Molar gas constant R = 8(31 J mol(1 K(1
Acceleration due to gravity at sea level g = 9(81 m s(2
Universal constant of gravitation G = 6(67 ( 10-11 N m2 kg-2
Planck constant h = 6(63 ( 10(34 J s
Speed of light in vacuo c = 3(00 ( 108 m s(1
Permittivity of free space (o = 8(85 ( 10(12 F m(1
Permeability of free space (o = 4( ( 10(7 H m(1
Stefan constant ( = 5(67 ( 10-8 W m2 K-4
Wien constant W = 2(90 ( 10-3 m K
Units
T / K = ( / (C + 273(15
1 u = 1(66 ( 10-27 kg
AS
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|(F = ma |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] | |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
| | |[pic] |
|[pic] | |
Particle Physics
| |Leptons | |Quarks |
|particle (symbol) |electron (e() |electron neutrino ((e) | |up (u) |down (d) |
|charge (e) |( 1 |0 | |[pic] |[pic] |
|Lepton number |1 |1 | |0 |0 |
A2
|[pic] |[pic] |[pic]and[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] or [pic] |
|[pic] |[pic] |[pic] or [pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |
|[pic] |[pic] | |
Fields
|[pic] |[pic] |[pic] |[pic] |
|[pic] |[pic] |[pic] |[pic] |
Orbiting Bodies
Centre of mass: [pic];
Period of Mutual Orbit: [pic]
Options
A: [pic]; [pic]; [pic]; [pic]; [pic]; [pic]
B: [pic]; [pic]
C: [pic]; [pic]; [pic]; [pic]
D: [pic]; [pic]
E: [pic]; [pic] [pic] Carnot efficiency[pic]
Mathematical Information
SI Multipliers
|Multiple |Prefix |Symbol | |Multiple |Prefix |Symbol |
|10-18 |atto |a | |103 |kilo |k |
|10-15 |femto |f | |106 |mega |M |
|10-12 |pico |p | |109 |giga |G |
|10-9 |nano |n | |1012 |tera |T |
|10-6 |micro |( | |1015 |peta |P |
|10-3 |milli |m | |1018 |exa |E |
|10-2 |centi |c | |1021 |zetta |Z |
Areas and volumes
Area of a circle [pic]; Area of a triangle = ½ base ( height
|Solid |Surface area |Volume |
|rectangular block |[pic] |[pic] |
|cylinder |[pic] |[pic] |
|sphere |[pic] |[pic] |
Trigonometry
[pic]; [pic]; [pic]; [pic]
PR2 = PQ2 + QR2
Logarithms (A2 only)
[Unless otherwise stated, ‘log’ can be loge (i.e. ln) or log10]
[pic] [pic]
[pic] [pic]
[pic]
ADVICE FOR CANDIDATES IN PRACTICAL PHYSICS
• Before commencing any question read the whole question through completely.
• You will be allowed 15 minutes to complete each Section A question. In this time you should complete all required calculations and written answers.
• You will be allowed 45 minutes to complete each Section B question. In this time you should complete all required calculations and written answers.
• Where possible, repeat all readings so that you may calculate the best value and uncertainty. If repeat readings are not required the question will state so. Record all readings, including repeat readings, and quote the appropriate units.
• Express any answers – including the gradients and intercepts of graphs – to an appropriate number of significant figures and with the appropriate units.
• Show all intermediate steps in calculations as credit will be given for a correct approach even if the final answer is incorrect.
• Where the question requires it, estimate the uncertainty and/or the percentage uncertainty in a measured or calculated quantity and express the quantity ± its uncertainty [see below].
Graphs
• Include a title and axes which are labelled with scales and units.
• Make sure the scales are convenient to use, so that readings may easily be taken from the graph – avoid scales which use factors of 3 – and that the plotted points occupy at least half of both the vertical and horizontal extent of the graph grid.
• Draw an appropriate best-fit line; consider carefully whether the data suggest that the appropriate line is straight or curved. Draw the appropriate line by eye rather than calculation – though you may want to calculate the centroid of the data points.
• When extracting data from a graph, use the best-fit line rather than the original data.
• When determining the gradient of a graph, show clearly on your graph the readings you use. This is most conveniently done by drawing a right angled triangle – this should be large so that accuracy is preserved.
Uncertainties
1. Expressing uncertainties
Use the form x ± u, where x is the quantity being measured and u its estimated uncertainty.
2. Estimating uncertainties using the resolution of an instrument.
If a single reading is taken and there is no reason to believe that the uncertainty is greater, take the uncertainty to be the instrument resolution.
3. Estimating uncertainties using the spread of readings.
Take the estimated uncertainty to be half the spread in the readings, discounting any anomalous readings.
i.e. [pic]
4. Percentage uncertainties
The percentage uncertainty, p, is calculated from:
[pic]
Uncertainties in calculated quantities
1. If a quantity is calculated by multiplying and/or dividing two or more other quantities, each of which has its own uncertainty, the percentage uncertainty is found by adding the percentage uncertainties.
e.g. If ( is calculated using [pic], the percentage uncertainty in ( is:
[pic].
2. If a quantity is calculated by multiplying by a constant, the percentage uncertainty is unchanged.
3. If a quantity is raised to a power, e.g. x2, x3 or [pic], the percentage uncertainty is multiplied by the same power.
Example of 2 and 3: The energy, E, stored in a stretched spring is given by[pic]. Both k and x have uncertainties, but [pic] has no uncertainty.
So [pic]
Guidance notes on experimental work.
Section 1 – Treatment of uncertainties in Physics at AS and A2 level
Preamble
One of the main aims of the practical work undertaken in GCE Physics is for candidates to develop a feeling for uncertainty in scientific data. Some of the treatment that follows may appear daunting. That is not the intention. The estimates of uncertainties that are required in this specification are more in the nature of educated guesses than statistically sound calculations.
Definitions
Uncertainty
Uncertainty in measurements is unavoidable and estimates the range within which the answer is likely to lie. This is usually expressed as an absolute value, but can be given as a percentage.
The normal way of expressing a measurement x0, with its uncertainty, u, is x0 ± u. This means that the true value of the measurement is likely to lie in the range x0 ( u to x0 + u.
Note: The term “error” is used in many textbooks instead of uncertainty. This term implies that something has gone wrong and is therefore best avoided.
Uncertainties can be split up into two different categories:
- Random uncertainties – These occur in any measured quantity. The uncertainty of each reading cannot be reduced by repeat measurement but the more measurements which are taken, the closer the mean value of the measurements is likely to be to the “true” value of the quantity. Taking repeat readings is therefore a way of reducing the effect of random uncertainties.
- Systematic uncertainties – These can be due to a fault in the equipment, or design of the experiment e.g. possible zero error such as not taking into account the resistance of the leads when measuring the resistance of an electrical component or use of a ruler at a different temperature from the one at which it is calibrated. The effect of these cannot be reduced by taking repeat readings. If a systematic uncertainty is suspected, it must be tackled either by a redesign of the experimental technique or theoretical analysis. An example of this sort of uncertainty, the origin of which remains mysterious, is in the determination of stellar distances by parallax. The differences between the distances, as determined by different observatories, often exceeds the standard uncertainties by a large margin.
Percentage uncertainty
This is the absolute uncertainty expressed as a percentage of the best estimate of the true value of the quantity.
Resolution
This is the smallest quantity to which an instrument can measure.
Mistake
This is the misreading of a scale or faulty equipment.
Anomalous points
These are points that lie well outside the normal range of results e.g. well away from a line or curve of best fit. They often arise from mistakes in measurement. These should be recorded and reason for discarding noted by the candidate.
How is the uncertainty in the measurement of a quantity estimated?
1. Estimation of uncertainty using the spread of repeat readings.
Suppose the value a quantity x is measured several times and a series of different values obtained:
x1, x2, x3……..xn. [Normally, in our work, n will be a small number, say 3 or 5].
Unless there is reason to suspect that one of the results is seriously out [i.e. it is anomalous], the best estimate of the true value of x is the arithmetic mean of the readings:
Mean value [pic]
A reasonable estimate of the uncertainty is ½ the range:
i.e. [pic], where [pic]is the maximum and [pic]the minimum reading of x [ignoring any anomalous readings]
Example
The following results were obtained for the time it took for an object to roll down a slope.
4.5 s, 4.8 s, 4.6 s, 5.1 s, 5.0 s
The best estimate of the true time is given by the mean which is:
[pic]
The uncertainty, u, is given by: [pic]
The final answer and uncertainty should be quoted, with units, to the same no. of decimal places and the uncertainty to 1 sig. fig
i.e. t = 4.8 ± 0.3 s
Note that, even if the initial results had be taken to the nearest 0.01 s, i.e. the resolution of an electronic stopwatch, the final result would still be given to 0.1 s because the first significant figure in the uncertainty is in the first place after the decimal point.
The percentage uncertainty, p [pic]. Again, p is only expressed to 1 s.f.
2. Estimation of uncertainty from a single reading
Sometimes there may only be a single reading. Sometimes all the readings may be identical. Clearly it cannot be therefore assumed that there is zero uncertainty in the reading(s).
With analogue instruments, it is not expected that interpolated readings will be taken between divisions (this is clearly not possible with digital instrument anyway). Hence, the uncertainty cannot be less than ½ the smallest division of the instrument being used, and is recommended it be taken to be ± the smallest division. In some cases, however, it will be larger than this due to other uncertainties such as reaction time [see later] and manufacturer’s uncertainties. If other sources of random uncertainty are present, it is expected that in most cases repeat readings would be taken and the uncertainty estimated from the spread as above.
Advice for Specific apparatus
Metre Rule
Take the resolution as ±1 mm. This may be unduly pessimistic, especially if care is taken to avoid parallax errors. It should be remembered that all length measurements using rules actually involve two readings – one at each end – both of which are subject to uncertainty. In many cases the uncertainty may be greater than this due to the difficulty in measuring the required quantity, for example due to parallax or due to the speed needed to take the reading e.g. rebound of a ball, in which case the precision could be ± 1 cm. In cases involving transient readings, it is expected that repeats are taken rather than relying on a guess as to the uncertainty.
Standard Masses
For 20g, 50g, 100g masses the precision can be taken as being as being ±1g this is probably more accurate than the manufacturer’s [often about 3%]. Alternatively, if known, the manufacturer’s uncertainty can be used.
Digital meters [ammeters/voltmeters]
The uncertainty can be taken as being ± the smallest measurable division. Strictly this is often too accurate as manufacturers will quote as bigger uncertainty. [e.g. 2% + 2 divisions]
Thermometers
Standard -10 ºC to 110 ºC take precision as 1ºC
Digital thermometers uncertainty could be ± 0.1ºC. However the actual uncertainty may be greater due to difficulty in reading a digital scale as an object is being heated or cooled, when the substance is not in thermal equilibrium with itself let alone with the thermometer.
The period of oscillation of a Pendulum/Spring
The resolution of a stop watch, used for measuring a period, is usually 0.01s. Reaction time would increase the uncertainty and, although in making measurements on oscillating quantities it is possible to anticipate, the uncertainty derived from repeat readings is likely to be of the order of 0.1 s. To increase accuracy, often 10 (or 20) oscillations are measured. The absolute error in the period [i.e. time for a single oscillation] is then 1/10 (or 1/20 respectively) of the absolute error in the time for 10 (20) oscillations
e.g. 20 oscillations: Time = 15.8 ± 0.1 s [0.6%]
( Period [pic]s = 0.790 ± 0.005 s
Note that the percentage uncertainty, p, in the period is the same as that in the overall time.
In this case, [pic](1 s.f.)
Digital vernier callipers/micrometer
Precision smallest measurable quantity usually ± 0.01mm.
Measuring cylinder / beakers/ burette
Smallest measurable quantity e.g. ± 1 cm³, but this depends upon the scale of the instrument. In the case of measuring the volume using the line on a beaker, the estimated uncertainty is likely to be much greater.
Note candidates must be careful to avoid parallax when taking these measurements, and should state that all readings were taken at eye level. They should also measure to the bottom of the meniscus.
Determining the uncertainties in derived quantities.
Please note that candidates entered for AS award will now be required to combine percentage uncertainties.
Very frequently in Physics, the values of two or more quantities are measured and then these are combined to determine another quantity; e.g. the density of a material is determined using the equation:
[pic]
To do this the mass, m, and the volume, V, are first measured. Each has its own estimated uncertainty and these must be combined to produce an estimated uncertainty in the density. The volume itself may have been determined by combining several independent quantity determinations [e.g. length, breadth and height for a rectangular solid or length and diameter for a cylindrical wire].
In most cases, quantities are combined either by multiplying or dividing and this will be considered first. Multiplying by a constant, squaring (e.g. in [pic]), square rooting or raising to some other power are special cases of this and will be considered next.
1. Multiplying and dividing:
The percentage uncertainty in a quantity, formed when two or more quantities are combined by either multiplication or division, is the sum of the uncertainties in the quantities which are combined.
Example
The following results were obtained when measuring the surface area of a glass block with a 30cm rule, resolution 0.1cm
Length = 9.7 ± 0.1 cm
Width = 4.4 ± 0.1cm
Note that these uncertainties are estimates from the resolution of the rule.
This gives the following percentage errors:
Length: [pic]
Width [pic]
So the percentage error in the volume, [pic]
Hence surface area = 9.7 ( 4.4 = 42.68 cm² ± 3.2 %
The absolute error in the surface area is now 3.2% of 42.68 = 1.37 cm²
Quoted to 1 sig. fig. the uncertainty becomes 1 cm²
The correct result, then, is 43 ± 1cm² - Note that surface area is expressed to a number of significant figures which fits with the estimated uncertainty.
2. Raising to a power (eg x2, x(1, [pic])
The percentage uncertainty in xn is n times the percentage uncertainty in x.
e.g. a period (T) is as being 31 seconds with a percentage uncertainty of 2 %,
So T2 = 961 ± 4%.
4% ( 961 = 40 (to 1.s.f)
So the period squared is expressed as T2 = 960 ± 40 s.
Note: x(1 is the same as 1/x. So the percentage uncertainty in 1/x is the same as that in x. Can you see why we ignore the ( sign?
Note: the percentage uncertainty in [pic]is half the percentage uncertainty in x.
3. Multiplying by a constant
In this case the percentage uncertainty is unchanged. So the percentage uncertainty in 3x or 0.5x or (x is the same as that in x.
Example: The following determinations were made in order to find the volume of a piece of wire:
Diameter: d = 1.22 ± 0.02 mm
Length: l = 9.6 ± 0.1 cm
The percentage uncertainties are: pd = 1.6%; pl = 1.0%.
Working in consistent units, and applying the equation [pic], we have:
V = 448.9 mm3
The percentage uncertainty, pV = 1.6 ( 2 + 1.0 = 4.2 % = 4 % (to 1 s.f.)
[Note that ( and 4 have no uncertainties.]
So the absolute uncertainty u = 448.9 ( 0.04 = 17.956 = 20 (1 s.f.)
So the volume is expressed as V = 450 ± 20 mm3.
4. Adding or subtracting quantities [A2 only]
If 2 quantities are added or subtracted the absolute uncertainty is added. This situation does not arise very frequently as most equations involve multiplication and division only. The e.m.f. / p.d. equation for a power supply is an exception.
In all cases, when the final % uncertainty is calculated it can then be converted back to an absolute uncertainty and quoted 1 sig. figure. The final result and uncertainty should be quoted to the same number of decimal places
GRAPHS [derivation of uncertainties from graphs is only expected in A2]
The following remarks apply to linear graphs:
The points should be plotted with error bars. These should be centred on the plotted point and have a length equal to ymax ( ymin [for uncertainties in the y values of the points]. If identical results are obtained the precision of the instrument could be used. If the error bars are too small to plot this should be stated.
If calculating a quantity such as gradient or intercept the steepest line and a least steep line should be drawn which are consistent with the error bars. It is often convenient to plot the centroid of the points to help this process. This is the point [pic], the mean x value against the mean y value. The steepest and least steep lines should both pass through this point.
.
The maximum and minimum gradients, mmax and mmin, [or intercepts, cmax and cmin] can now be found and the results quoted as:
gradient = [pic]
intercept = [pic]
Scales
Graph should cover more than ½ of the graph paper available and awkward scales [e.g. multiples of 3] should be avoided. Rotation of the paper through (/2 [90( !] may be employed to give better coverage of the graph paper.
Semi-log and log-log graphs [A2 only]
Students will be expected to be familiar with plotting these graphs as follows:
Semi-log: to investigate relationships of the form: [pic].
Taking logs: [pic] or [pic] [It doesn’t matter which]
So a plot of [pic] against x has a gradient [pic] and an intercept [pic].
Examples: Radioactive or capacitor decay, oscillation damping
Log-log: to investigate relationships of the form: [pic]
Taking logs: [pic] [or the equivalent with natural logs]
So a plot of [pic] against [pic]has a gradient n and an intercept [pic].
Examples: Cantilever depression or oscillation period as a function of overhang length, Gallilean moon periods against orbital radius to test relationship.
Note that Log-log or semi-log graph paper will not be required.
Uncertainties from Log graphs: Candidates will not be expected to include error bars in log plots.
Section 2 – Experimental techniques
The following is a selection of experimental techniques which it is anticipated that candidates will acquire during their AS and A2 studies. It is not exhaustive, but is intended to provide some guidance into the expectations of the PH3 and PH6 experimental tasks.
Measuring instruments
The use of the following in the context of individual experiments:
• micrometers and callipers. These may be analogue or digital. It is intended that candidates will have experience of the use of these instruments with a discrimination of at least 0.01 mm. A typical use is the determination of the diameter of a wire.
• digital top-loading balances.
• measuring cylinders and burettes. This is largely in the context of volume and density determination.
• force meters (Newton meters).
• stop watches with a discrimination of 0.01 s. It is also convenient to use stopwatches / clocks with a discrimination of 1 s.
• rules with a discrimination of 1 mm.
• digital multimeters with voltage, current and resistance ranges. The following (d.c.) ranges and discriminations illustrative the ones which are likely to be useful:
2 V 0.001 V
20 V 0.01 V
10 A 0.01 A
2 A 0.001 A
2 k( 1 (
200 ( 0.01 (
Students should be familiar with the technique of starting readings on a high range to protect the instrument.
• liquid in glass thermometers. -10 ( 110(C will normally suffice, though candidates can be usefully introduced to the advantages of restricted range thermometers. Where appropriate, digital temperature probes may be used.
Experimental techniques
The purpose of PH3 is to test the ability of the candidates to make and interpret measurements, with special emphasis on:
• combining measurements to determine derived values, eg density or internal resistance
• estimating the uncertainty in measured and derived quantities
• investigating the relationships between variables
These abilities will be developed by centres, using all the content of PH1 and PH2. They can and will be assessed using very simple apparatus which can be made available in multiple quantities. Hence it is not foreseen that apparatus which centres are likely to possess in small numbers, if at all, will be specified, e.g. oscilloscopes, data loggers, travelling microscopes.
The following list may be found useful as a checklist. Candidates should be familiar with the following techniques:
• connecting voltmeters across the p.d. to be determined, i.e. in parallel;
• connecting ammeters so that the current flows through them, i.e. in series;
• the need to avoid having power supplies in circuits when a resistance meter is being employed;
• taking measurements of diameter at various places along a wire / cylinder and taking pairs of such measurements at right angles to allow for non-circular cross sections;
• determining a small distance measurement, e.g. the thickness or diameter of an object, by placing a number of identical objects in contact and measuring the combined value, e.g. measuring the diameter of steel spheres by placing 5 in line and measuring the extent of the 5;
• the use of potentiometers (N.B. not metre wire potentiometers) and variable resistors in circuits when investigating current-voltage characteristics;
• the determination of the period and frequency of an oscillating object by determining the time taken for a number of cycles [typically 10 or 20]; N.B. Although the concept of period is not on the AS part of the specification, it is likely to be used in PH3;
• the use of fiducial marks and no-parallax in sighting against scales and in period determinations.
SUMMARY OF ASSESSMENT
This specification is divided into a total of 6 units: 3 AS units and 3 A2 units. Weightings noted below are expressed in terms of the full A level qualification.
AS (3 units)
|PH1 20% 1¼ hour Written Paper 80 marks[120 UM] |
|Motion, Energy & Charge |
| |
|Approx 7 structured questions. No question choice. No sections. |
|PH2 20% 1¼ hours Written Paper 80 marks [120 UM] |
|Waves & Particles |
|Approx 7 structured questions. No question choice. No sections. |
|PH3 10% Internal Assessment 48 marks [60 UM] |
|Practical Physics |
| |
|Experimental tasks, performed under controlled conditions, based upon experimental techniques |
|developed in the AS course. |
A LEVEL (the above plus a further 3 units)
|PH4 18% 1¼ hour Written Paper 80 marks [108 UM] |
|Oscillations & Fields |
| |
|Approx 7 questions. Includes synoptic assessment. No question choice. No sections. |
|PH5 22% 1¾ hour written paper 100 marks[132 UM] |
|Electromagnetism, Nuclei and Options |
| |
|Section A: Approximately 5 questions on the compulsory content of the unit. 60 marks |
|Section B: Case Study, synoptic in nature, based upon open-source material distributed by the |
|board. 20 marks |
|Section C: Options: Alternating Currents, Revolutions, Materials, Medical Physics, Energy. 20 |
|marks |
|PH6 10% Internal Assessment [UMS = 60] |
|Experimental & Synoptic Assessment |
| |
|An experimental task (25 marks), and a data-analysis task (25 marks) performed under controlled |
|conditions, both synoptic in nature. |
• Synoptic assessment is included in PH4 and PH5. It is inherent in the internal assessment PH6
PHYSICS
1 INTRODUCTION
1. 1 Criteria for AS and A Level GCE
This specification has been designed to meet the general criteria for GCE Advanced Subsidiary (AS) and A level (A) and the subject criteria for AS/A Physics as issued by the regulators [July 2006]. The qualifications will comply with the grading, awarding and certification requirements of the Code of Practice for 'general' qualifications (including GCE).
The AS qualification will be reported on a five-grade scale of A, B, C, D, E. The A level qualification will be reported on a six-grade scale of A*, A, B, C, D, E. The award of A* at A level will provide recognition of the additional demands presented by the A2 units in term of 'stretch and challenge' and 'synoptic' requirements. Candidates who fail to reach the minimum standard for grade E are recorded as U (unclassified), and do not receive a certificate. The level of demand of the AS examination is that expected of candidates half way through a full A level course.
The AS assessment units will have equal weighting with the second half of the qualification (A2) when these are aggregated to produce the A level award. AS consists of three assessment units, referred to in this specification as PH1, PH2 and PH3. A2 also consists of three units, referred to as PH4, PH5 and PH6.
Assessment units may be retaken prior to certification for the AS or A level qualifications, in which case the better result will be used for the qualification award. Individual assessment unit results, prior to certification for a qualification, have a shelf-life limited only by the shelf-life of the specification.
The specification and assessment materials are available in English and Welsh.
1.2 Progression
This specification provides a suitable foundation for the study of Physics, Engineering, Medicine or a related area through a range of higher education courses or direct entry into employment. In addition, the specification provides a coherent, satisfying and worthwhile course of study for candidates who do not progress to further study in this subject.
1.3 Rationale
The specification for AS and A-level Physics complies with the GCE AS and A Subject Criteria for Science Subjects, published by CCEA, DELLS and QCA. It provides
(a) a complete course in Physics to GCE A level;
(b) a firm foundation in Physics knowledge and understanding, together with mathematical competence for those wishing proceed to further studies in Physics, Engineering, Mathematics, Medicine or the Natural Sciences.
Students who follow the specification will be introduced to a wide range of Physics principles and be led to an understanding of how nature operates at both microscopic and macroscopic scales. They will understand how these principles are applied in tackling problems of human society.
1.4 The Wider Curriculum
Physics is a subject that by its nature requires candidates to consider individual, ethical, social, cultural and contemporary issues. The specification provides a framework for exploration of such issues and includes specific content through which educators may address these issues; for example, the use of radioactive isotopes in medicine, the discussion on nuclear power and the environmental consequences of the use of fossil fuels.
The specification contains topics which allow teachers within Wales to draw upon Welsh examples and priorities in line with the Curriculum Cymreig, for example in the development of energy resources.
1.5 Equality and Fair Assessment
AS/A levels often require assessment of a broad range of competences. This is because they are general qualifications and, as such, prepare candidates for a wide range of occupations and higher level courses.
The revised AS/A level qualification and subject criteria were reviewed to identify whether any of the competences required by the subject presented a potential barrier to any disabled candidates. If this was the case, the situation was reviewed again to ensure that such competences were included only where essential to the subject. The findings of this process were discussed with disability groups and with disabled people.
In GCE Physics practical assistants may be used for manipulating equipment and making observations. Technology may help visually impaired students to take readings and make observations.
Reasonable adjustments are made for disabled candidates in order to enable them to access the assessments. For this reason, very few candidates will have a complete barrier to any part of the assessment. Information on reasonable adjustments is found in the Joint Council for Qualifications document Regulations and Guidance Relating to Candidates who are eligible for Adjustments in Examinations. This document is available on the JCQ website (.uk).
Candidates who are still unable to access a significant part of the assessment, even after exploring all possibilities through reasonable adjustments, may still be able to receive an award. They would be given a grade on the parts of the assessment they have taken and there would be an indication on their certificate that not all of the competences have been addressed. This will be kept under review and may be amended in future.
2 AIMS
The AS and A specifications in Physics aim to encourage students to:
(a) develop an enthusiasm for Physics and, where appropriate to pursue this enthusiasm in its further study;
(b) understand the processes of Physics, as a Natural Science, the way the subject develops through experiment, theory, insight and creative thought;
(c) appreciate the role of Physics in society, in particular how its discoveries are applied in industry and medicine and how decisions about its use are made;
(d) appreciate the interconnectedness of the subject and the ways in which different strands of Physics can be used to solve problems and gain new insights into the natural world;
(e) acquire a more general understanding of the way in which scientific disciplines make progress, acquire and interpret evidence, propose and evaluate solutions, communicate ideas and interact with society, as outlined in section 3.6, How Science Works, of the GCE AS and A level criteria for Science Subjects.
How science Works
In the context of AS/A Physics, candidates should:
• use theories, models and ideas to develop and modify scientific explanations;
• use knowledge and understanding to pose scientific questions, define scientific problems, present scientific arguments and scientific ideas;
• use appropriate methodology, including ICT, to answer scientific questions and solve scientific problems;
• carry out experimental and investigative activities, including appropriate risk management, in a range of contexts;
• analyse and interpret data to provide evidence, recognising correlations and causal relationships;
• evaluate methodology, evidence and data, and resolve conflicting evidence;
• appreciate the tentative nature of scientific knowledge;
• communicate information and ideas in appropriate ways using appropriate terminology;
• consider applications and implications of science and appreciate their associated benefits and risks;
• appreciate the role of the scientific community in validating new knowledge and ensuring integrity;
• appreciate the ways in which society uses physics knowledge and practice to inform decision-making.
3 ASSESSMENT OBJECTIVES
Weightings
Assessment objective weightings are shown below as % of the full A level, with AS weightings in brackets.
|Unit |raw marks |unit % weighting |
| |Unit total |AO1 |AO2 |AO3 | |
|PH2 |80 |35 |35 |10 |20 (40) |
|PH3 |48 |4 |4 |40 |10 (20) |
|PH4 |80 |30 |40 |10 |18 |
|PH5 |100 |34 |60 |6 |22 |
|PH6 |50 |5 |5 |40 |10 |
|Total AS% |37 |37 |27 |
|Total A2% |30 |46 |23 |
|Total A% |34 |42 |25 |
4 SPECIFICATION CONTENT
4.1 Units SI units will be used throughout this specification. Knowledge of SI multipliers will be required. A table of the SI multipliers will be included in each examination paper.
4.2 Practical Work Practical work will play an important role throughout the course. Attention is drawn to the specified content in each unit and the instructions relating to the practical internal assessments.
4.3 Mathematical
requirements The following list of requirements is taken from the GCE AS and A level Criteria for Science Subjects [July 2006]. The sections in bold type [i.e. use of radians, the exponential and log functions] will not be required at AS level, because the subject content which requires these concepts is not met in this part of the course.
Candidates will be required to:
4.3.1 Computation
• recognise and use expressions in decimal and standard form
• use ratios, fractions and percentages
• use calculators to find and use power, exponential and logarithmic functions
• use calculators to handle sin x, cos x, tan x when x is expressed in degrees or radians
4.3.2 Handling data
• use an appropriate number of significant figures
• find arithmetic means
• make order of magnitude calculations.
4.3.3 Algebra
• understand and use the symbols: =, , (, ~
• change the subject of an equation
• substitute numerical values into algebraic equations using appropriate units for physical quantities
• solve simple algebraic equations
4.3.4 Graphs
• translate information between graphical, numerical and algebraic forms
• plot two variables from experimental or other data
• understand that y = mx + c represents a linear relationship
• determine the slope and intercept of a linear graph
• draw and use the slope of a tangent to a curve as a measure of rate of change
• understand the possible physical significance of the area between a curve and the x axis and be able to calculate it or measure it by counting squares as appropriate
• use logarithmic plots to test exponential and power law variations
• sketch simple functions including y = k/x, y = kx2, y = k/x2,
y = sin x, y = cos x, y = e-x
4.3.5 Geometry and Trigonometry
• calculate areas of triangles, circumferences and areas of circles, surface areas and volumes of rectangular blocks, cylinders and spheres
• use Pythagoras' theorem, and the angle sum of a triangle
• use sin, cos and tan in physical problems
• understand the relationship between degrees and radians and translate from one to the other.
Advanced Subsidiary
PH1 Assessment Unit – MOTION, ENERGY & CHARGE
The Unit is built around a core relating to the following Subject Criteria content:
S3.3 (a) – (d) Mechanics
S4.4(a) – (d) Electrical Circuits
SPECIFICATION
PH1.1 BASIC PHYSICS
Content
• Units and dimensions
• Scalar and vector quantities
( Force
( Free body diagrams
( Movements and stability
( Equilibrium
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall and use SI units,
(b) check equations for homogeneity using units,
(c) contrast scalar and vector quantities and give examples of each – displacement, velocity, acceleration, force, speed, time, density, pressure etc.,
(d) appreciate the concept of force and understand Newton's 3rd law of motion,
(e) use free body diagrams to represent forces on a particle or body,
(f) recall and use the relationship (F = ma in situations where mass is constant,
(g) add and subtract coplanar vectors, and perform mathematical calculations limited to two perpendicular vectors,
(h) resolve a vector into two perpendicular components,
(i) understand the concept of density, use the equation [pic]to calculate mass, density and volume;
(j) understand and define the turning effect of a force;
(k) recall and use the principle of moments;
(l) understand and use centre of gravity, for example in simple problems including toppling and stability. Identify its position in a cylinder, sphere and cuboid (beam) of uniform density;
(m) understand that a body is an equilibrium when the resultant force is zero and the net moment is zero, and be able to perform simple calculations.
PH1.2 KINEMATICS
Content
• Rectilinear motion.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) define displacement, mean and instantaneous values of speed, velocity and acceleration,
(b) use graphical methods to represent displacement, speed, velocity and acceleration,
(c) understand and use the properties of displacement-time graphs, velocity-time graphs, acceleration-time graphs, and interpret speed and displacement-time graphs for non-uniform acceleration,
(d) derive and use equations which represent uniformly accelerated motion in a straight line,
(e) describe the motion of bodies falling in a gravitational field with and without air resistance ( terminal velocity,
(f) recognise and understand the independence of vertical and horizontal motion of a body moving freely under gravity,
(g) describe and explain motion due to a uniform velocity in one direction and uniform acceleration in a perpendicular direction, and perform simple calculations.
PH1.3 ENERGY CONCEPTS
Content
• Work, Power and Energy.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall the definition of work as the product of a force and distance moved in the direction of the force when the force is constant; calculation of work done, for constant forces, when force is not along the line of motion ([pic])
(b) understand that the work done by a varying force is the area under the Force-distance graph,
(c) recall and use Hooke's law F = kx, and apply this to (b) above to show that elastic potential energy is [pic]Fx or [pic]kx2,
(d) understand and apply the work – energy relationship
[pic]and recall that Ek = [pic]mv2,
(e) recall and apply the principle of conservation of energy including use of gravitational potential energy [pic], elastic potential energy [pic]kx2, and kinetic energy [pic]mv2,
(f) define power as the rate of energy transfer,
(g) appreciate that dissipative forces e.g. friction, viscosity, cause energy to be transferred from a system and reduce the overall efficiency of the system,
(h) recall and use Efficiency = [pic]
PH1.4 CONDUCTION OF ELECTRICITY
Content
• Electric charge.
• Electric current.
• Nature of charge carriers in conductors.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) understand how attraction and repulsion between rubbed insulators can be explained in terms of charges on the surfaces of these insulators, and that just two sorts of charge are involved;
(b) understand that the name negative charge was arbitrarily given to the sort of charge on an amber rod rubbed with fur, and positive to that on a glass rod rubbed with silk;
(c) recall that electrons can be shown to have a negative charge, and protons, a positive;
(d) explain frictional charging in terms of electrons removed from, or added to, surface atoms;
(e) recall that the unit of charge is the coulomb (C), and that an electron's charge, e, is a very small fraction of a coulomb;
(f) recall that charge can flow through certain materials, called conductors;
(g) understand that electric current is rate of flow of charge;
(h) recall and use the equation [pic];
(i) recall that current is measured in ampère (A), where A = Cs-1;
(j) understand and describe the mechanism of conduction in metals as the drift of free electrons;
(k) derive and use the equation I = nAve for free electrons.
PH1.5 RESISTANCE
CONTENT
• Relationship between current and potential difference.
• Resistance
• Resistivity.
• Variation of resistance with temperature for metals.
• Superconductivity
• Heating effect of an electric current.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) define potential difference and recall that its unit is the volt (V) where V = JC-1.
(b) sketch I – V graphs for a semiconductor diode, the filament of a lamp, and a metal wire at constant temperature;
(c) state Ohm's Law;
(d) define resistance;
(e) recall that the unit of resistance is the ohm (Ω), where Ω = VA-1;
(f) understand that collisions between free electrons and ions give rise to electrical resistance, and to a steady drift velocity under a given p.d.,
(g) recall and use[pic] and understand that this is the defining equation for resistivity;
(h) describe how to determine the resistivity of a metal experimentally;
(i) describe how to investigate experimentally the variation of resistance with temperature of a metal wire;
(j) recall that the resistance of metals varies almost linearly with temperature over a wide range;
(k) understand what is meant by superconductivity, and superconducting transition temperature;
(l) recall that not all metals show superconductivity, and that, for those that do, the transition temperatures are a few degrees above absolute zero (–273°C);
(m) recall that certain special materials (high temperature superconductors) have transition temperatures above the boiling point of nitrogen (–196°C), and can therefore be kept below their transition temperatures using liquid nitrogen;
(n) recall that superconducting magnets are used in particle accelerators, tokamaks and magnetic resonance imaging machines, and are expected soon to be used in some large motors and generators;
(o) understand that ordinarily (that is, above the transition temperature), collisions between free electrons and ions in metals increase the random vibration energy of the ions, so the temperature of the metal increases;
(p) recall and use [pic].
PH1.6 D.C. CIRCUITS
CONTENT
• Series and parallel circuits.
• Combination of resistors.
• The internal resistance of sources.
• The potential divider.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) understand and recall that the current from a source is equal to the sum of the currents in the separate branches of a parallel circuit, and that this is a consequence of conservation of charge;
(b) understand and recall that the p.d.s across components in a series circuit is equal to the p.d. across the supply, and that this is a consequence of conservation of energy;
(c) understand and recall that the p.d.s across components in parallel are equal;
(d) recall and use formulae for the combined resistance of resistors in series and parallel;
(e) derive and use the potential divider formula [pic];
(f) define the e.m.f. of a source and appreciate that its unit, the volt (V), is the same as that of potential difference.
(g) appreciate that sources have internal resistance and use the formula
V = E − Ir
(h) calculate current and p.d.s in a simple circuit containing one cell or cells in series.
PH2 Assessment Unit – WAVES & PARTICLES
The Unit is contains the following Subject Criteria content:
3.5 Waves
3.7 (a) – (b) Quantum physics: photons, particles
SPECIFICATION
PH2.1 WAVES
Content
• Progressive waves.
• Transverse and longitudinal waves.
• Polarisation.
• Frequency, wavelength and velocity of waves.
• Diffraction.
• Interference.
• Two-source interference patterns.
• Stationary waves.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) understand that a progressive wave transfers energy or information from a source to a detector without any transfer of matter;
(b) distinguish between transverse and longitudinal waves,
(c) describe experiments which demonstrate the polarisation of light and microwaves;
(d) explain the terms displacement, amplitude, wavelength, frequency, period and velocity of a wave,
(e) draw and interpret graphs of displacement against time, and displacement against position for transverse waves only,
(f) recall and use the equation c = f(,
(g) be familiar with experiments which demonstrate the diffraction of water waves, sound waves and microwaves, and understand that significant diffraction only occurs when ( is of the order of the dimensions of the obstacle or slit,
(h) state, explain and use the principle of superposition,
(i) describe an experimental demonstration of two-source interference for light, appreciating the historical importance of Young's experiment, and be familiar with experiments which demonstrate two source interference for water waves, sound waves and microwaves;
(j) use the equation [pic] for double-slit interference,
(k) show an understanding of path difference, phase difference, and coherence,
(l) state the conditions necessary for two-source interference to be observed, i.e. constant phase difference, vibrations in the same line,
(m) recall the shape of the intensity pattern from a single slit and its effect on double-slit and diffraction grating patterns,
(n) use the equation d sin [pic] = n( for a diffraction grating,
(o) give examples of coherent and incoherent sources,
(p) describe experiments which demonstrate polarisation of light,
(q) be familiar with experiments which demonstrate stationary waves, e.g. vibrations of a stretched string and for sound in air,
(r) state the differences between stationary and progressive waves,
(s) understand that a stationary wave can be regarded as a superposition of two progressive waves of equal amplitude and frequency, travelling in opposite directions and that the internodal distance is [pic]
PH2.2 REFRACTION OF LIGHT
Content
• Refraction.
• Wave Model of Refraction
• Optical Fibre Communications
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall and use Snell's Law of refraction;
(b) recall and use the equations
[pic];
(c) understand how Snell's Law relates to the wave model of light propagation;
(d) understand the conditions for total internal reflection and derive and use the equation for the critical angle
[pic];
(e) apply the concept of total internal reflection to multimode optical fibres;
(f) appreciate the problem of multi-mode dispersion with optical fibres in terms of limiting the rate of data transfer and transmission distance;
(g) explain how the introduction of monomode optical fibres has allowed for much greater transmission rates and distances;
(h) compare optical fibre communications to terrestrial microwave links, satellite links and copper cables for long distance communication.
PH2.3 PHOTONS
Content
• The photoelectric effect.
• Photons
• The electromagnetic spectrum
• Line emission and line absorption spectra
• X-rays
• Spontaneous and stimulated emission
• Lasers – energy levels and structure
• The semiconductor laser and its uses
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) describe how the photo-electric effect can be demonstrated
(b) describe how the maximum kinetic energy, KEmax, of emitted electrons can be measured, using a vacuum photocell;
(c) sketch a graph of KEmax against frequency of illuminating radiation;
(d) understand and recall how a photon picture of light leads to Einstein's equation, [pic] and how this equation correlates with the graph of Ekmax against frequency;
(e) describe in outline how X-rays are produced in an X-ray tube, and sketch a graph of intensity against wavelength;
(f) recall the characteristic properties and orders of magnitude of the wavelengths of the radiations in the electromagnetic spectrum;
(g) calculate typical photon energies for these radiations;
(h) understand in outline how to produce line emission and line absorption spectra from atoms;
(i) describe the appearance of such spectra as seen in a diffraction grating;
(j) understand and use atomic energy level diagrams, together with the photon hypothesis, to explain line emission and line absorption spectra;
(k) calculate ionisation energies from an energy level diagram;
(l) understand and explain the process of stimulated emission and how this process leads to light emission that is coherent;
(m) understand the concept of population inversion (Note: for A level students the condition N2 > N1 will suffice) and explain that population inversion is necessary for a laser to operate;
(n) understand that population inversion is not (usually) possible with a 2-level energy system;
o) understand how population inversion is attained in 3 and 4-level energy systems;
p) understand the process of pumping and its purpose;
q) recall the structure of a typical laser i.e. an amplifying medium between two mirrors, one of which partially transmits light;
r) know the basic structure of a semiconductor diode laser;
s) know that laser systems are far less than 1% efficient in general (usually around 0.01% efficient) due to pumping losses but that semiconductor lasers can obtain 70% efficiency and that pumping requires the application of a p.d. of around 3V;
t) know the advantages and uses of a semiconductor laser i.e. small, cheap, efficient and used for CDs, DVDs, telecommunication etc.
PH2.4 MATTER, FORCES AND THE UNIVERSE.
Content
• The nuclear atom
• Leptons and Quarks
• Particle interactions
• Conservation Laws
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) describe a simple model for the nuclear atom in terms of nucleus and electrons orbiting in discrete orbits, explaining the composition of the nucleus in terms of protons and neutrons and expressing the nuclear and atomic structures using the [pic]notation
(b) recall that matter is composed of quarks and leptons – the following information will be available to candidates in examinations:
| |Leptons | |Quarks |
|particle (symbol) |electron (e() |electron neutrino ((e) | |up |down |
| | | | |(u) |(d) |
|charge (e) |( 1 |0 | |[pic] |[pic] |
[N.B. No questions will be set involving generations higher than generation 1.]
(c) recall that antiparticles exist to the particles given in the table above, that the properties of an antiparticle are identical to that of its corresponding particle apart from having opposite charge, and that particles and antiparticles annihilate; use the above table to give the symbols of the antiparticles;
(d) recall the following information about the four forces or interactions, which are experienced by particles:
|Interaction |Experienced by |Range |Comments |
|Gravitational |all particles |infinite |very weak – negligible except in the|
| | | |context of large objects such as |
| | | |planets and stars |
|Weak |all particles |very short range |only significant in cases where the |
| | | |electromagnetic and strong |
| | | |interactions do not operate |
|Electromagnetic |all charged |infinite |also experienced by neutral hadrons |
| |particles | |because they are composed of quarks |
|Strong |quarks |short range |experienced by quarks and particles |
| | | |composed of quarks |
(e) recall that quarks are never observed in isolation, but bound into composite particles called hadrons, which are classified as either baryons (e.g. the proton or neutron) which consist of 3 quarks or mesons (e.g. pions) which consist of a quark-antiquark pair;
(f) use tables of data to suggest the quark structure of given baryons or mesons;
(g) understand that, in particle interactions, charge and lepton number are conserved.
PH2.5 USING RADIATION TO INVESTIGATE STARS
Content
• Black-body radiation
• Wien's displacement law – stellar temperatures
• Stefan's law and stellar luminosity
• Intensity and the inverse square law
• Fraunhofer lines and stellar composition
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall that a stellar spectrum consist of a continuous emission spectrum, from the dense gas of the surface of the star, and a line absorption spectrum arising from the passage of the emitted electromagnetic radiation through the tenuous atmosphere of the star,
(b) recall that bodies which absorb all incident radiation are known as black bodies and that stars are very good approximations to black bodies,
(c) recall the shape of the black body spectrum and that the peak wavelength is inversely proportional to the absolute temperature (defined by T/K = (/(C + 273(15) – Wien's displacement law;
(d) use Wien's displacement law, Stefan's Law and the inverse square law to investigate the properties of stars – luminosity, size, temperature and distance [N.B. stellar brightness in magnitudes will not be required];
(e) interpret data on stellar line spectra to identify elements present in stellar atmospheres;
(f) recall that the analysis of stellar spectra reveals that roughly 75% of the universe, by mass, is Hydrogen and 24% Helium, with very small quantities of the other elements;
(g) recall the main branch of the proton-proton chain, which is th[pic]e main energy production mechanism in stars like the Sun:
[pic]
and that neutrinos from the first step of this chain can be detected on Earth;
PH3 Internal Assessment Unit – PRACTICAL PHYSICS
This Unit gives candidates opportunities to demonstrate development of their experimental, manipulative, interpretative and communication skills.
SPECIFICATION
Candidates are required to undertake, under controlled conditions, a set of experimental tasks. The tasks are devised by the WJEC and assessed by the supervisor using a marking scheme provided by the WJEC.
AMPLIFICATION OF CONTENT
Candidates should be able to:
• follow instructions and plan experimental activities,
• make observations and draw conclusions,
• take measurements and record data showing awareness of the limits of accuracy and correct use of significant figures,
• assess the uncertainty in measurements and derived quantities,
• present data in different forms, including graphically,
• analyse and interpret data, demonstrating appropriate knowledge and understanding of physics, and investigate the relationships between physical quantities,
• evaluate experimental techniques and outcomes,
• communicate experimental findings clearly using SI units.
Task details
• Measuring instrument requirements will include items expected to be found in a school laboratory [see section 8 – Guidance on Internal Assessment].
• Other equipment requirements will include standard laboratory items such as clamp stands and slotted masses, but may also include items which need to be obtained specially for the assessment from equipment suppliers or D.I.Y. stores.
• Detailed requirements for the assessment will be issued to centres two months prior to the assessment. The information provided will give the context of the task and detailed instructions on measuring instruments required, and assemblage of apparatus.
• The assessment is in two sections: Section A and Section B.
Section A consists of 3 short items, each of duration 15 minutes. These items concentrate on making measurements, determining the magnitude of quantities and the associated uncertainty. The contexts are from across the AS specification. The 3 items each carry 8 marks.
Section B consists of a single item of duration 45 minutes. Candidates are expected to undertake an investigation into the relationship between quantities. Section B carries 24 marks.
There is no requirement for candidates to undertake the items in any specific order.
• Centres are free to organise the progression of candidates between the items as they wish, but the timings lend themselves to assessing candidates in multiples of 6, with 3 candidates being engaged in Section A [tackling the items in a cycle] and 3 in Section B at any one time.
• Centres are issued with a marking scheme for the assessment of candidates’ responses. The results should be forwarded to the WJEC and the candidates’ work presented for moderation in line with the procedures of the WJEC.
Advanced Level
PH4 Assessment Unit – OSCILLATIONS & FIELDS
Advanced Level A2
The Unit is built around a core relating to the following Subject Criteria content:
3.3 (e) – (g) Mechanics: momentum, circular motion, oscillations
3.6 Matter: molecular kinetic theory, internal energy
3.8 (a) Fields: force fields
SPECIFICATION
PH4.1 VIBRATIONS
Content
• Circular motion
• Physical and mathematical treatment of undamped simple harmonic motion.
• Energy interchanges during simple harmonic motion.
• Damping of oscillations.
• Free oscillations, forced oscillations and resonance.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) understand and use period of rotation, frequency, the radian measure of angle,
(b) define and use angular velocity [pic],
(c) recall and use[pic] and hence [pic]
(d) define simple harmonic motion as a statement in words,
(e) recall, recognise and use [pic] as a mathematical defining equation of simple harmonic motion,
(f) illustrate, and interpret graphically, the variation of acceleration with displacement during simple harmonic motion,
(g) recall and use [pic] as a solution to [pic],
(h) explain the terms frequency, period, amplitude and phase [pic],
(i) recall and use the period as [pic],
(j) recall and use [pic]for the velocity during simple harmonic motion,
(k) illustrate, and interpret graphically, the changes in displacement and velocity with time during simple harmonic motion,
(l) recall and use the equation [pic] for the period of a system having stiffness (force per unit extension) k and mass m,
(m) illustrate, and interpret graphically, the interchange between kinetic energy and potential energy during undamped simple harmonic motion, and perform simple calculations on energy changes,
(n) explain what is meant by free oscillations and understand the effect of damping in real systems,
(o) describe practical examples of damped oscillations, and the importance of critical damping in appropriate cases such as vehicle suspensions,
(p) explain what is meant by forced oscillations and resonance, and describe practical examples,
(q) sketch the variation of the amplitude of a forced oscillation with driving frequency and know that increased damping broadens the resonance curve,
(r) appreciate that there are circumstances when resonance is useful e.g. circuit tuning, microwave cooking and other circumstances in which it should be avoided e.g. bridge design.
PH4.2 MOMENTUM CONCEPTS
Content
• Linear momentum.
• Newton's laws of motion.
• Conservation of linear momentum; particle collision.
• The momentum of a photon
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) define linear momentum as the product of mass and velocity,
(b) recall Newton's laws of motion and know that force is rate of change of momentum, applying this in situations where mass is constant,
(c) state the principle of conservation of momentum and use it to solve problems in one dimension involving elastic collisions (where there is no loss of kinetic energy) and inelastic collisions (where there is loss of kinetic energy).
(d) use the formula for the momentum of a photon: [pic];
(e) appreciate that the absorption or reflection of photons gives rise to radiation pressure.
PH4.3 THERMAL PHYSICS
Content
• Ideal gas laws and the equation of state.
• Kinetic theory of gases.
• The kinetic theory of pressure of a perfect gas
• Internal energy.
• The internal energy of an ideal gas
• Energy transfer.
• First law of thermodynamics.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall and use Boyles law for an ideal gas,
(b) recall and use the equation of state for an ideal gas expressed as pV = nRT where R is the molar gas constant, and understand that this equation can be used to define the Kelvin scale of temperature and the absolute zero of temperature,
(c) recall the assumptions of the kinetic theory of gases which includes the random distribution of energy among the particles,
(d) explain how molecular movement causes the pressure exerted by a gas, and understand and use [pic] where N is the number of molecules,
(e) define the Avogadro constant NA and hence the mole;
(f) understand that the molar mass M is related to the relative molecular mass Mr by M/kg = Mr/1000, and that the number of moles n is given by [pic];
(g) compare [pic] with pV = nRT and deduce that the total translational kinetic energy of a mole of a monatomic gas is given by [pic] and hence the average kinetic energy of a molecule is [pic] where [pic] is the Boltzmann constant, and deduce that T is proportional to the mean kinetic energy
(h) understand that the internal energy of a system is the sum of the potential and kinetic energies of its molecules;
(i) understand that the internal energy of an ideal monatomic gas is wholly kinetic so is given by [pic]
(j) understand that heat enters or leaves a system through its boundary or container wall, according to whether the system's temperature is lower or higher than that of its surroundings, so heat is energy in transit and not contained within the system;
(k) understand that if no heat flows between systems in contact, then they are said to be in thermal equilibrium, and are at the same temperature;
(l) understand that energy can also enter or leave a system by means of work, so work is also energy in transit;
(m) use [pic] to calculate the work done by a gas under constant pressure;
(n) understand and explain that, even if p changes, W is given by the area under the p – V graph;
(o) recall and use the first law of thermodynamics, in the form [pic], knowing how to interpret negative values of (U, Q, and W.
(p) understand that for a solid (or liquid), W is usually negligible, so [pic];
(q) use the formula[pic], for a solid or liquid, understanding that this is the defining equation for specific heat capacity, c.
PH4.4 ELECTROSTATIC AND GRAVITATIONAL FIELDS OF FORCE
Content
• Electrostatic and gravitational fields.
• Field strength (intensity).
• Electrical and gravitational inverse square laws.
• Potential in force fields.
• Relation between force and potential energy gradient.
• Relation between intensity and potential gradient
•. Field lines and equipotential surfaces.
• Vector addition of electric fields.
• Potential energy of a system of charges.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall the main features of electric and gravitational fields as specified in the table overleaf,
(b) recall that the gravitational field outside spherical bodies such as the earth is essentially the same as if the whole mass were concentrated at the centre
(c) understand that field lines (or lines of force) give the direction of the field at a point, thus, for a positive point charge, the field lines are radially outward; and that equipotential surfaces join points of equal potential and are therefore spherical for a point charge
(d) calculate the net potential and resultant field strength for a number of point charges and point masses,
(e) appreciate that ΔUP = mgΔh for distances over which the variation of g is negligible.
|REQUIREMENT |ELECTRIC FIELDS |GRAVITATIONAL FIELDS |
|Define … |electric field strength, E, as the force per unit charge on a small |gravitational field strength, g, as the force per unit mass on a |
| |positive test charge placed at the point, |small test mass placed at the point, |
|Recall and use the inverse square law for the force between |two electric charges in the form |two masses in the form |
| |[pic] where [pic] (Coulomb's Law) |[pic] where k = G (Newton's Law of Gravitation) |
|Recall that |F can be attractive or repulsive |F is attractive only |
|Recall and use … |[pic]for the field strength due to a point charge in free space or |[pic] for the field strength due to a point mass |
| |air | |
|Define potential at a point due to … |a point charge in terms of the work done in bringing unit positive |a point mass in terms of the work done in bringing a unit mass from |
| |charge from infinity to that point, |infinity to that point, |
|Recall and use the equations…. |[pic] |[pic] |
|• Know that the change in potential energy of … |a point charge moving in any electric field |a point mass moving in any gravitational field |
|• Use these relationships. |[pic] |[pic] |
|• Recall that the field strength at a point is given by … |E = - slope of the VE – r graph at that point |g = - slope of the Vg– r graph at that point, and for uniform fields.|
|• Use these relationships. | | |
|• Know that the potential difference is given by … |the area under the E – r graph. |the area under the g – r graph. |
PH4.5 APPLICATION TO ORBITS IN THE SOLAR SYSTEM AND THE WIDER UNIVERSE
Content
• Kepler's Laws of Planetary Motion
• Circular orbits of satellites, planets and stars
• Centre of Mass
• Missing mass in galaxies – Dark Matter
• Objects in mutual orbit
• Doppler shift of spectral lines
• Extra-solar planets
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) state Kepler's three Laws of Planetary Motion,
(b) recall and use Newton's law of Gravitation [pic] in simple examples, including the motion of planets and satellites;
(c) derive Kepler's 3rd Law, for the case of a circular orbit from Newton's Law of Gravity and the formula for centripetal acceleration,
(d) use data on orbital motion, such as period or orbital speed, to calculate the mass of the central object;
(e) appreciate that the orbital speeds of objects in spiral galaxies implies the existence of dark matter;
(f) calculate the position of the centre of mass of two spherically-symmetric objects, given their masses and separation, and calculate their mutual orbital period in the case of circular orbits,
(g) use the Doppler relationship in the form [pic];
(h) calculate a star's radial velocity (i.e. the component of its velocity along the line joining it and an observer on the Earth) from data about the Doppler shift of spectral lines,
(i) use data on the variation of the radial velocities of the bodies in a double system (e.g. a star and orbiting planet) and their orbital period to determine the masses of the bodies for the case of a circular orbit edge on as viewed from the Earth
PH5 Assessment Unit – MAGNETISM, NUCLEI & OPTIONS
Advanced Level A2
The Unit is built around a core relating to the following Subject Criteria content:
3.4 (e) Electrical circuits: capacitance
3.7 (c) – (d) Nuclear Physics: nuclear decay, nuclear energy
3.8 (b) – (c) Fields: B-fields, flux and electromagnetic induction
SPECIFICATION
PH5.1 CAPACITANCE
Content
• The parallel plate capacitor.
• Concept of capacitance.
• Factors affecting capacitance.
• Energy stored in a capacitor.
• Capacitors in series and parallel.
• Capacitor discharge.
AMPLIFICATION OF CONTENT
Candidates should be able to:
a) understand that a simple parallel plate capacitor consists of a pair of equal parallel metal plates separated by vacuum or air,
(b) understand that the capacitor stores energy by transferring charge from one plate to the other, so that the plates carry equal but opposite charges (the net charge being zero),
(c) define capacitance as [pic],
(d) use [pic] for a parallel plate capacitor, with no dielectric,
(e) know that a dielectric increases the capacitance of a vacuum-spaced capacitor;
(f) recall that the E field within a parallel plate capacitor is uniform and of value V/d,
(g) use the equation [pic] for the energy stored in a capacitor,
(h) use formulae for capacitors in series and in parallel,
(i) understand the process by which a capacitor discharges through a resistor,
(j) use the equation
[pic]where RC is the time constant.
PH5.2 B-FIELDS
Content
• Concept of magnetic fields (B-fields).
• Force on a current-carrying conductor.
• Force on a moving charge.
• Magnetic fields due to currents.
• Effect of a ferrous core.
• Force between current – carrying conductors.
• Definition of the ampere.
• Measurement of magnetic field strength B.
• Deflection of beams of charged particles in electric and magnetic fields.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) predict the direction of the force on a current-carrying conductor in a magnetic field,
(b) define magnetic field B by considering the force on a current-carrying conductor in a magnetic field; recall and use
F = BIl sin [pic],
(c) use [pic] for a moving charge in a magnetic field;
(e) understand the processes involved in the production of a Hall voltage and understand that VH ( B for constant I.
(f) describe how to investigate steady magnetic fields with a Hall probe,
(g) sketch the magnetic fields due to a current in
(i) a long straight wire,
(ii) a long solenoid,
(h) use the equations [pic]and [pic] for the field strengths due to a long straight wire and in a long solenoid,
(i) know that adding an iron core increases the field strength of a solenoid,
(j) explain why current-carrying conductors exert a force on each other and predict the directions of the forces,
(k) understand how the equation for the force between two currents in straight wires leads to the definition of the ampere,
(m) describe quantitatively how ion beams, i.e. charged particles, are deflected in uniform electric and magnetic fields,
(o) apply knowledge of the motion of charged particles in magnetic and electric fields to linear accelerators, cyclotrons and synchrotrons.
PH5.3 ELECTROMAGNETIC INDUCTION
Content
• Magnetic flux.
• Laws of electromagnetic induction.
• Calculation of induced emf.
• Self induction.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall and define magnetic flux as [pic] and flux linkage = [pic]
(b) recall the laws of Faraday and Lenz,
(c) recall and use e.m.f. = – rate of change of flux linkage and use this relationship to derive an equation for the e.m.f. induced in a linear conductor moving at right angles to a uniform magnetic field,
(e) relate qualitatively the instantaneous e.m.f. induced in a coil rotating at right angles to a magnetic field to the position of the coil, flux density, coil area and angular velocity;
(f) understand and use the terms frequency, period, peak value and root-mean-square value when applied to alternating voltages and currents,
(g) understand that the r.m.s. value is related to the energy dissipated per cycle, and use the relationships [pic] and [pic]
(h) recall that the mean power dissipated in a resistor is given by
[pic], where V and I are the r.m.s. values;
(i) describe the use of a cathode ray oscilloscope to measure:
(ii) a.c. and d.c. voltages and currents,
(iii) frequencies.
PH5.4 RADIOACTIVITY AND RADIOISOTOPES
Content
• Radioactive decay.
• Half-life.
• Applications of radioactivity.
• Hazards and safety precautions.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) recall the spontaneous nature of nuclear decay; describe the nature of α, β and γ radiation, and use equations to represent the nuclear transformations using the [pic] notation,
(b) describe methods used to distinguish between (, ( and ( radiation and explain the connections between the nature, penetration and range for ionising particles,
(c) account for the existence of background radiation and make allowance for this in experimental measurements,
(d) explain what is meant by half-life [pic],
(e) define activity A and the becquerel,
(f) define decay constant ([pic]) and recall and use the equation A = –[pic]N.
(g) recall and use the exponential law of decay in graphical and algebraic form,
[[pic]
where x is the number of half-lives elapsed – not necessarily an integer,]
(h) derive and recall that [pic],
(i) describe briefly the use of radioisotopes (any two applications),
(j) show an awareness of the biological hazards of ionising radiation e.g. whether exposed to external radiation or when radioactive materials are absorbed (ingestion and/or inhalation).
PH5.5 NUCLEAR ENERGY
Content
• Binding Energy.
• Fission and Fusion.
• Nuclear Reactors.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) appreciate the association between mass and energy and recall that [pic],
(b) calculate the binding energy for a nucleus and hence the binding energy per nucleon, making use, where necessary, of the unified atomic mass unit (u) and the electron-volt (eV),
(c) apply the conservation of mass/energy to particle interactions – e.g. fission, fusion and neutrino detection interactions
(d) describe the relevance of binding energy per nucleon to nuclear fission and fusion,
(e) explain how neutron emission gives the possibility of a chain reaction,
(f) understand and describe induced fission by thermal neutrons and the roles of moderator, control rods and coolants in thermal reactors,
(g) understand and recall the factors influencing choice of materials for moderator, control rods and coolant,
(i) discuss the environmental problems posed by the disposal of the waste products of nuclear reactors.
OPTIONAL CONTENT IN UNIT A2
The following section contains the 5 optional sections to A2. It is anticipated that candidates will study only one of these optional topics. The approximate teaching time required for each option is 15 hours. The questions on the optional topics will occupy a separate section in the PH5 paper and account for 20 marks.
Option A2/A Further Electromagnetism and Alternating Currents
Content
• Mutual induction.
• Simple treatment of the transformer.
• Self induction and self inductance
• A.C. behaviour of a capacitor and an inductor; reactance, mean power.
• Vector treatment of RC, RL and RCL series circuits; impedance.
• Uses: simple RC filters, tuned circuits.
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) describe, in terms of electromagnetic induction, how a changing current in one coil induces an e.m.f. in another coil;
(b) understand that a closed-loop iron core enables a real transformer to approximate to the ideal case where there is no flux leakage;
(c) understand and recall that that if there is no flux leakage, or voltage drops in the primary or secondary, then [pic];
(d) understand and recall that if there were no energy dissipation in the transformer itself, then [pic], in which the p.d.s and currents are r.m.s. values;
(e) recall that in practice there is some energy dissipation due to
(i) the resistance of the primary and secondary coils,
(ii) eddy currents in the iron core,
(iii) energy used cyclically to change the magnetisation of the core;
(f) recall that these losses can be reduced by
(i) using thick enough wires for the coils,
(ii) laminating the core,
(iii) choosing a suitable alloy for the core;
(g) describe, in terms of electromagnetic induction, how a changing current in a coil induces in that coil an e.m.f., whose direction is such as to oppose the change in current;
(h) define the self-inductance of a coil by the equation [pic];
(i) understand the 90° phase lag of current behind p.d. for an inductor in a sinusoidal a..c. circuit;
(j) recall that [pic] is called the reactance, [pic], of the inductor, and use the equation [pic];
(k) understand the 90° phase lead of current ahead of p.d. for a capacitor in a sinusoidal a..c. circuit, and use the equation[pic];
(l) recall that the mean power dissipation in an inductor or a capacitor is zero;
(m) add p.d.s across series RC, RL and RCL combinations using phasors;
(n) calculate phase angle and impedance, Z, (defined as [pic]) for such circuits;
(o) derive an expression for the resonance frequency of an RCL series circuit;
(p) understand that the sharpness of the resonance curve is determined by the ratio [pic], known as the Q factor of the circuit;
(q) understand how a series LCR circuit can be used to select frequencies;
(r) understand how a CR circuit can be used as a simple high-pass or low-pass filter;
Option A2/B Revolutions in Physics
This option module consists of two topics.
Topics
• The Newtonian Revolution
• Electromagnetism and Space-Time
AMPLIFICATION OF CONTENT
1. The Newtonian Revolution
General Approach
• Why do things move in the way they do? How our concepts of force and motion developed during the seventeenth century, culminating with Newton's Principia.
• The course is structured around the study of some 10 short extracts from the (translated) works of the giants of the revolution, including Kepler, Descartes and Galileo, as well as Newton himself.
• Questions about the nature of science will arise and invite discussion e.g. can an abstract mathematical law really be said to explain what makes the planets move in ellipses?
• WJEC will provide teachers' notes, including guidance on what to look for in the extracts.
• In examinations, candidates would be expected to recognise, say, a diagram from Newton or Descartes, or a paragraph from Galileo and to comment on its significance. This wouldn't, of course, be the only sort of question.
Ground to be Covered
• The official (post-Aristotle) view of the 'perfect', eternal, circular motion of heavenly bodies and the short-lived motion of bodies (like carts and arrows) on the Earth.
• Ptolemy's earth-centred universe and Copernicus's Sun-centred system
• Kepler's elliptical orbits.
• Galileo: the Law of Inertia and the heliocentric system made plausible.
• Descartes: A mechanistic universe of particles and contact forces, including the vortex theory of the solar system. No place for occult forces and influences in Descartes' world?
• Newton's 'shoulders of giants' synthesis: the link between force and motion, how a central force can account for planetary motion, the inverse square law, celestial and terrestrial dynamics unified…
• Questions raised: Did Newton really explain anything? Was Newton satisfied with his own work? What were the effects of the Newtonian revolution on the way people thought? Has Newton's work been superseded? …
2. Electromagnetism and Space-Time
General Approach
• This course sketches how the evidence was uncovered for light being an electromagnetic wave, and how this preceded revolutionary changes in our views of time and space.
• The study of some eight shortish extracts from the works of Young, Faraday, Maxwell, Hertz and others will help to give the course structure. In examinations, candidates would be expected to recognise a diagram or a paragraph from these extracts and to comment on its significance.
• Questions about the nature of science will arise and invite discussion e.g. Can science and common sense be at odds?
• WJEC will provide teachers' notes, including guidance on what to look for in the extracts.
Ground to be Covered
• The background: exciting work in Physics around 1800: Young's resurrection of the wave theory of light, Galvani's twitching frog's leg and Volta's pile.
• Oersted's discovery that an electric current gives rise to a magnetic field and Ampère's quantitative work.
• Faraday's lines of force, tending to contract along their length and to expand sideways, explaining the forces of coils or magnets (or charges) on one another – contrasted with the 'action at a distance' theories of Ampère and others.
• Faraday's discovery of electromagnetic induction.
• Maxwell's espousal of Faraday's lines of force as physical things and a glimpse of his early 'vortex' model, which led to his prediction of electromagnetic waves with the same speed as light – surely not a co-incidence.
• Maxwell's realisation that the testable Physics in his model could all be summed up in four [sets of] equations, so the model itself could be ditched.
• Hertz: Maxwell vindicated.
• The aether: a medium needed for the propagation of light and other e-m waves? The purpose and principle and result of the Michelson-Morley experiment.
• Einstein's Special Relativity accounts naturally for this result. A simple thought experiment on time dilation to give a flavour of the theory.
Option A2/C Materials
Content
• Hooke's Law
• Stress-strain and the Young Modulus
• Strain energy – elastic hysteresis
• Elastic and plastic behaviour
• Composite materials
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) Classify solids as crystalline, amorphous and polymeric in terms of their microscopic structure.
(b) Describe an experiment to investigate the behaviour of a spring in terms of load and extension, recall and use Hooke's law and define the spring constant as force per unit extension. [pic]
(c) Define tensile stress [pic]and tensile strain [pic]and the Young modulus and perform simple calculations; compare the Young modulus of various solids
(d) Describe an experiment to determine the Young modulus of a metal in the form of a wire.
(e) Deduce the strain energy in a deformed solid material from the area under a force/extension graph [pic]and recall and derive the equation: strain energy per unit volume [pic] and apply to cases in which K.E is absorbed by a wire or rope.
(f) Describe the main features of force/extension, stress/strain graphs for ductile materials such as copper and compare these with less ductile metals such as steel.
(g) Describe the deformation of ductile materials at the molecular level and distinguish between elastic and plastic strain.
(h) Describe, at the molecular level, the effect of dislocations and the strengthening and stiffening of materials by the introduction of dislocation barriers such as foreign atoms, other dislocations and grain boundaries;
(i) understand, on a simple molecular level, how superalloys have been developed to withstand extreme conditions, and describe some of their uses;
(j) Describe in molecular terms failure mechanisms in ductile materials: ductile fracture (necking), creep and fatigue.
(k) Understand that heat treatment processes may control the mechanical properties of metals: cold working (work hardening), annealing (e.g. copper) and quench hardening (e.g. steel)
(l) Demonstrate an understanding of the force/extension, stress/strain graph for a brittle substance such as glass and be able to compare it with the graph for a ductile material.
(m) Describe brittle fracture in molecular terms and the effect of surface imperfections on breaking stress (UTS) and the increased breaking stress of thin glass fibres.
(n) Describe thermoplastic (e.g. polythene) and thermosetting (e.g. melamine) polymers at the molecular level. Compare and contrast their properties and describe some of their uses.
(o) Demonstrate an understanding of the force/extension, stress/strain graph for polymeric substances (rubber and polyethylene).
(p) Compare the behaviour of rubber and polyethylene in terms of molecular structure and behaviour under stress with reference also to the effect of temperature. Understand the importance of hysteresis in rubber.
(q) Recall that materials do not always behave in a similar way in tension and compression and that crack propagation is more difficult under compression- with particular reference to concrete and prestressed glass as examples.
(r) Understand that composite materials are developed to take advantage of the mechanical properties of the individual materials from which they are made, with reference to vehicle tyres, reinforced concrete, fibre reinforced polymers (e.g. glass and carbon) and wood based composites used as examples.
Option A2/D Biological Measurement and Medical Imaging
Content
• X-rays
• Ultrasound
• Magnetic resonance imaging
• Nuclear imaging
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) describe the nature and properties of X-rays.
(b) describe the production of X-ray spectra including methods of controlling the beam intensity, photon energy, image sharpness, contrast and patient dosage.
(c) describe the use of high energy X-rays in the treatment of patients (therapy) and low energy X-rays in diagnosis.
(d) use the equation [pic] for the attenuation of X-rays;
(e) understand the use of X-rays to give images of internal structures, image intensifiers and contrast media.
(f) describe the use of a rotating beam CT scanner (computerised axial tomography).
(g) describe the generation and detection of Ultrasound using piezoelectric transducers;
(h) describe scanning with Ultrasound for diagnosis including A-scans and B-scans (use of real time B-scans is not required) incorporating examples and applications;
(i) understand the significance of acoustic impedance, defined by [pic] for the reflection and transmission of sound waves at tissue boundaries, including appreciating the need for a coupling medium;
(j) understand the use of the Doppler equation [pic] to study blood flow using an ultrasound probe.
(k) understand the principles of magnetic resonance with reference to precession nuclei, resonance and relaxation time.
(l) describe the use of the MRI in obtaining diagnostic information about internal structures.
(m) discuss the advantages and disadvantages of ultra sound imaging, X-ray imaging and MRI in examining internal structures;
(n) understand the structure of the heart as a double pump
(o) describe methods of detecting electrical signals at the skin surface.
(p) describe the basic method of operation of an ECG machine, and explain the characteristic waveform by considering the heart's response to a potential originating at the sino-atrial node;
(q) describe the effects of α, β, and γ radiation on living matter.
(r) define and use the Gray (Gy) as the unit of absorbed dose and the sievert (Sv) as the unit of dose equivalent
(s) describe uses of radionuclides as tracers to image body parts with particular reference to I-123 and I-131.
(t) describe the use of the gamma camera including the principles of the collimator, scintillation counter and photomultiplier.
(u) understand the principles of positron emission tomography (PET) scanning and its use in detecting tumours.
Option A2/E ENERGY MATTERS
This Option addresses energy in the real world. While the main emphasis is on the physics of energy producing and conserving processes, candidates should have an awareness of current energy issues (economic, environmental, humanitarian and political) together with an overview of key statistics and trends. A typical examination question might consist of a topical passage of from which students will draw conclusions, extract data for calculations etc. Much of the underlying physics is straightforward and will have been treated earlier in the specification as indicated below:
PH1.3 Energy concepts
PH1.5 Resistance
PH2.1 Waves
PH2.3 Photons
PH2.5 Matter forces and the universe (a) to (d)
PH4.3 Thermal physics
PH5.5 Nuclear energy.
Content
• Renewable energy sources
• Energy storage
• Nuclear, fossil and other non-renewable energy sources
• Hazards and harmful consequences
• Mass transfer processes
• Energy transfer processes
• Work from heat
AMPLIFICATION OF CONTENT
Candidates should be able to:
(a) estimate hydroelectric, tidal and wind power from simple mechanical models;
(b) be aware of existing and intended projects: hydroelectric
(e.g. Yangtze); tidal (e.g. La Rance, Severn); wind (e.g. London Array);
(c) understand the principle of energy storage in projects such as Ffestiniog and Dinorwig;
(d) interpret equations representing fission and fusion reactions, and calculate resulting energies from given mass data;
(e) understand the principles underlying breeding and enrichment in nuclear fission applications;
(f) show an understanding of the difficulties in producing sustained fusion power and be aware of current progress (JET) and prospects (ITER);
(g) recognise convection as mass movement of fluids and understand that energy losses by convection can be minimised by, for example, trapping gas in bubbles;
(h) understand and apply the thermal conduction equation in the form [pic] (derivation and recall not required);
(i) be aware of the origin and means of transmission of solar energy, and the form of the sun’s power spectrum;
(j) recall and use the Stefan-Boltzman T4 law and the Wien displacement law;
(k) understand what is meant by, and calculate, the Solar Constant from the sun’s temperature and geometrical formulae in the maths datasheet;
(l) be aware of the problems in harnessing solar energy and the limitations of solar cells;
(m) recognise the environmental effects of carbon fuels and understand the basis of the greenhouse effect;
(n) understand the principles of fuel cell operation and appreciate the benefits of fuel cells particularly regarding greenhouse gas emission;
(o) understand the principles underlying the ideal heat engine, the Carnot cycle, refrigerators and heat pumps (including recent applications e.g. the Cardiff Senedd);
(p) state and explain the second law of thermodynamics (Kelvin form); understand how the second law places an upper limit on the efficiencies of heat engines, for example of the turbines in conventional and nuclear power stations.
PH6 Internal Assessment Unit – Experimental Physics
This unit gives candidates the opportunity of demonstrating their ability to carry out their own investigations and to analyse and evaluate secondary experimental data. The unit is entirely synoptic in character.
AMPLIFICATION OF CONTENT
Candidates should be able to:
• plan and carry out an investigation at a level appropriate to the A2 course;
• analyse and evaluate data from their own investigation and from secondary sources using graphical and mathematical techniques including those specific to the A2 course;
• combine uncertainties arising from various measurements and judge which uncertainties are the most significant in a procedure;
Task Details
Candidates are required to undertake individually, under controlled conditions, two tasks: Task A and Task B. The tasks are devised by the WJEC, undertaken under controlled conditions and the outcomes assessed by the centre using marking schemes provided by the WJEC.
Task A: Data Analysis
This is a 45 minute task, carrying 25 marks. Candidates are provided with a set of experimental data on a topic drawn from the A level specification. They are given details of how the data were obtained. They will be expected to:
• analyse the data graphically and algebraically in order to establish a relationship between the variables and/or to derive a significant quantity – the graphical and analytic techniques may involve log-log or semi-log plots and the use of powers (positive or negative);
• derive an uncertainty from the graphical and/or algebraic analysis and express the solution in SI units to a precision commensurate with the uncertainty;
• make appropriate comments upon the analysis.
Task B: Investigation
This is a 75 minute task, carrying 25 marks. Candidates are provided with a set of apparatus and an experimental problem. They will be expected to:
• plan the safe use of some or all of the apparatus to investigate the problem (15 minutes);
• carry out their planned investigation, including analysing their data, drawing conclusions and evaluating both the data and the experimental techniques (1 hour).
In order to make the task discriminating and also to allow all candidates to make progress, provision is made for the supervisor to provide extra information where necessary. The provision of such information will result in marking penalties.
Both tasks will be carried out in the second half of the spring term. The details for the timing of the tasks and the receipt of the appropriate information will be given in the WJEC booklet Manual of Internal Assessment which is produced annually.
The candidates’ work is marked by the supervisor. The results are be forwarded to the WJEC and the candidates’ work presented for moderation in line with the procedures of the WJEC.
5 SCHEME OF ASSESSMENT
Synoptic Assessment
Synoptic assessment, testing candidates' understanding of the connections between the different elements of the subject and their holistic understanding of the subject, is a requirement of all A level specifications. In the context of Physics this means:
PH4: The work on vibrations, thermodynamics, electric and gravitation fields and potentials and the Doppler shift of spectral lines, builds upon concepts built up in the AS course. Questions examine these synoptic aspects.
PH5: All compulsory areas of this unit draw upon work in previous units: e.g. capacitors on electrical circuits (PH1) and electric fields (PH4); motion of charges in magnetic fields on circular motion (PH4); nuclear properties on particles (PH2). Questions are set which link these themes. The Case Study (section B) is synoptic in nature.
PH6: All aspects of the two parts of this internally-assessed unit are synoptic in nature.
Quality of Written Communication
Candidates will be required to demonstrate their competence in written communication in all assessment units where they are required to produce extended written material: PH2, PH5 and PH6. Mark schemes for these units include the following specific criteria for the assessment of written communication.
( legibility of text; accuracy of spelling, punctuation and grammar; clarity of meaning;
( selection of a form and style of writing appropriate to purpose and to complexity of subject matter;
( organisation of information clearly and coherently; use of specialist vocabulary where appropriate.
The front pages of all the external assessment papers include an emboldened statement informing candidates of the necessity for expressing themselves clearly using correct technical terms. The marking schemes covers include a statement of the requirement to take level of language into account and the detailed marking key indicates, using (QWC) places where the quality of the written communication will contribute to the assessment f performance.
Awarding, Reporting and Re-sitting
The overall grades for the GCE AS qualification will be recorded as a grade on a scale from A to E. The overall grades for the GCE A level qualification will be recorded on a grade scale from A* to E. Results not attaining the minimum standard for the award of a grade will be reported as U (Unclassified). Individual unit results and the overall subject award will be expressed as a uniform mark on a scale common to all GCE qualifications (see table below). The grade equivalence will be reported as a lower case letter ((a) to (e)) on results slips, but not on certificates:
| |Max. UMS |A |B |C |D |E |
|PH1 & PH2 |120 |96 |84 |72 |60 |48 |
|(weighting 20%) | | | | | | |
|PH3 & PH6 |60 |48 |42 |36 |30 |24 |
|(weighting 10%) | | | | | | |
|PH4 |108 |86 |76 |65 |54 |43 |
|(weighting 18%) | | | | | | |
|PH5 |132 |106 |92 |79 |66 |53 |
|(weighting 22%) | | | | | | |
|AS Qualification |300 |240 |210 |180 |150 |120 |
|A Qualification |600 |480 |420 |360 |300 |240 |
At A level, Grade A* will be awarded to candidates who have achieved a Grade A in the overall A level qualification and an A* on the aggregate of their A2 units.
Candidates may re-sit units prior to certification for the qualification, with the best of the results achieved contributing to the qualification. Individual unit results, prior to certification of the qualification have a shelf-life limited only by the shelf-life of the specification.
Glossary
|Item |Definition |
|Activity A. |The rate of decay (number of disintegrations per second) of a sample of radioactive nuclei. |
|Becquerel Bq. |Unit: Bq=s-1. |
|Ampere A. |The ampere is that constant current which when flowing through two infinite, thin, parallel |
| |wires, one metre apart in vacuum, produces a force between the wires of 2(10-7N per metre |
| |of length. Unit: A. |
|Amplitude |The amplitude is defined as the maximum displacement of any particle from its equilibrium |
| |position. |
|Amplitude A of an oscillating |The maximum value of the object’s displacement (from its equilibrium position). |
|object | |
|Angular velocity ω. |For a point describing a circle at uniform speed, the angular velocity ω is equal to the |
| |angle θ swept out by the radius in time t divided by t . (ω= θ/t) UNIT: [rad] |
| |s-1 |
|Atomic mass number, A |The atomic mass number of an atom is the number of nucleons (number of protons + number of |
| |neutrons) in its nucleus. |
|Atomic number, Z. |The atomic number of an atom is the number of protons in its nucleus. [This determines the |
| |chemical element which the atom represents.] |
|Avogdadro constant NA. |This is the number of particles in a mole. (NA=6.02(1023 to 3 figs). |
|Binding energy of a nucleus. |The energy that has to be supplied in order to dissociate a nucleus into its constituent |
| |nucleons. [It is therefore not energy which a nucleus possesses.] Unit: J [or MeV] |
|Boyle’s law |For a fixed mass of gas at constant temperature, the pressure varies inversely as the |
| |volume. (p = k/V) |
|Capacitor, reactance of. |When an AC voltage is applied to a capacitor, the reactance is given by XC = Vrms/Irms where|
| |Vrms and Irms are, respectively, the voltage across and the current ‘through’ the capacitor.|
| |It is equal to 1/(C (or 1/2(fC). |
|Capacitor. |A pair of parallel metal plates, a small distance apart, insulated from one another. |
|Centre of gravity. |The centre of gravity is the single point within a body at which the entire weight of the |
| |body is considered to act. |
|Coherence |Waves or wave sources, which have a constant phase difference between them (and therefore |
| |must have the same frequency) are said to be coherent. |
|Conservation of energy (principle|Energy cannot be created or destroyed, only transformed from one form to another. |
|of). | |
|Damping. |Damping is the dying away of amplitude with time of free oscillations due to resistive |
| |forces. |
|De Broglie relationship λ = h/p |The key relationship relating to wave-particle duality. It gives the wavelength λ associated|
| |with a moving particle in terms of its linear momentum p and the Planck constant h. |
|Decay constant λ. |The constant which appears in the exponential decay law [pic]and determines the rate of |
| |decay (the greater λ is, the more rapid the rate of decay). It is related to half life by λ |
| |= ln2/[pic]. |
| |Unit: s-1 |
|Displacement |The displacement of a point B from a point A is the shortest distance from A to B, together |
| |with the direction. UNIT: m. |
|e.m.f. |The e.m.f. of a source is the energy converted from some other form (e.g. chemical) to |
| |electrical potential energy per coulomb of charge flowing through the source. Unit: volt (V)|
| |[= JC-1]. |
|Efficiency |% Efficiency = 100((Useful energy obtained)/(Total energy input). |
|Elastic collision. |A collision in which there is no loss of kinetic energy. |
|Electric current, I. |This is the rate of flow of electric charge. I = ∆Q/∆t. |
| |Unit: A |
|Electric field strength E. |The force experienced per unit charge by a small positive charge placed in the field. Unit: |
| |Vm-1. |
|Electric potential VE. |Electric potential at a point is the work done per unit charge in bringing a positive charge|
| |from infinity to that point. Unit: V. [= JC-1] |
|Electrical Resistance, R. |The resistance of a conductor is the p.d. (V) placed across it divided by the resulting |
| |current (I) through it. R = V / I Unit: ohm (Ω) [= VA-1]. |
|Electron volt (eV). |This is the energy transferred when an electron moves between two points with a potential |
| |difference of 1 volt between them. 1 eV = 1.6 × 10-19 J |
| |[Within the context of particle accelerators it can also be defined as: the energy acquired |
| |by an electron when accelerated through a pd of 1V.] |
|Electron volt. (eV) |This is the energy transferred when an electron moves between two points with a potential |
| |difference of 1 volt between them. 1 eV = 1.6 × 10-19 J |
|Energy |The energy of a body or system is the amount of work it can do. UNIT: joule (J). |
|Faraday’s law |When the flux linking an electrical circuit is changing, an emf is induced in the circuit of|
| |magnitude equal to the rate of change of flux. |
|Flux linkage NФ. |If the above coil consists of N turns, the flux linkage is given by NФ. Unit: Wb or Wb |
| |turn. |
|Forced oscillations. |These occur when a sinusoidally varying force is applied to an oscillatory system, causing |
| |the system to oscillate with the frequency of the applied force. |
|Free oscillations. |Free oscillations occur when an oscillatory system (such as a mass on a spring, or a |
| |pendulum) is displaced and released. |
| |[The frequency of the free oscillations is known as the natural frequency.] |
|Frequency f. |The number of circuits or cycles per second. |
|Frequency of a wave |The frequency of a wave is the number of cycles of a wave that pass a given point in one |
| |second, |
| |or equivalently |
| |The frequency of a wave is the number of cycles of oscillation performed by any particle in |
| |the medium through which the wave is passing. |
|Gravitational field strength g. |The force experienced per unit mass by a mass placed in the field. Unit: ms-2 or Nkg-1. |
|Gravitational potential Vg. |Gravitational potential at a point is the work done per unit mass in bringing a mass from |
| |infinity to that point. |
| |Unit: Jkg-1. |
|Half life[pic][pic][pic][pic] |The time taken for the number of radioactive nuclei N (or the activity A) to reduce to one |
| |half of the initial value. Unit: s. |
|Hooke’s Law |The tension in a spring or wire is proportional to its extension from its natural length, |
| |provided the extension is not too great. |
|Hooke’s Law. |The extension of an elastic object such as a wire or spring is proportional to the |
| |stretching force, provided the extension is not too large. |
| |(F = kx). |
|Ideal gas. |An ideal gas strictly obeys the equation of state |
| |pV = nRT. |
|Inductor, reactance of. |When an AC voltage is applied to an inductor, the reactance is given by XL = Vrms/Irms where|
| |Vrms and Irms are, respectively, the voltage across and the current through the inductor. |
| |It is equal to (L (or 2(fL) |
|Inelastic collision. |A collision in which kinetic energy is lost. |
|Instantaneous Acceleration |The instantaneous acceleration of a body is its rate of change of velocity. UNIT: ms-2 |
|Instantaneous Speed |instantaneous speed = rate of change of distance |
| |UNIT: ms-1. |
|Instantaneous Velocity |The velocity of a body is the rate of change of displacement. |
| |UNIT: ms-1 |
|Intensity of a wave |Energy per second passing normally through a given area |
| |Area |
|Internal energy |The internal energy (of say a container of gas) is the sum of the potential and kinetic |
| |energies of the molecules. |
|Ionisation |The removal of one or more electrons from an atom. |
|Ionisation energy |The ionization energy of an atom is the minimum energy needed to remove an electron from the|
| |atom. Unit: J |
|Isotope. |Isotopes are atoms with the same number of protons, but different numbers of neutrons in |
| |their nuclei. |
|Lenz’s Law. |The direction of any current resulting from an induced emf is such as to oppose the change |
| |in flux linkage that is causing the current. |
|Longitudinal wave |A longitudinal wave is one where the particle oscillations are in line with (parallel to) |
| |the direction of travel (or propagation) of the wave. |
|Magnetic flux density B. |A length l of wire perpendicular to a magnetic flux density B, carrying a current I, |
| |experiences a force of magnitude BIl. Unit: T (Tesla) [= NA-1m-1] |
|Magnetic flux Ф. |If a single-turn coil of wire encloses an area A, and a magnetic field B makes an angle θ |
|Weber Wb. |with the normal to the plane of the coil, the magnetic flux through the coil is given by Ф =|
| |AB cos θ. Unit: Wb=Tm2. |
|Mean Acceleration |Mean Acceleration = [pic] |
| |UNIT: ms-2. |
|Mean Speed |Mean speed = [pic] |
| |UNIT: ms-1. |
|Mean Velocity |Mean velocity = [pic] |
| |UNIT: ms-1. |
|Mole. |This is the amount of substance that has the same number of particles (usually atoms or |
| |molecules), as there are atoms in exactly twelve grammes of the nuclide [pic]. |
|Momentum |The momentum of an object is its mass multiplied by its velocity. (p = mv). It is a vector. |
| | |
| |UNIT: kg m s-1 |
|Newton’s law of gravitation. |The gravitational force between two objects is directly proportional to the product of their|
| |masses and inversely proportional to the distance between their centres. F = Gm1m2/r2 |
|Newton’s Laws of Motion. 1st Law |An object continues in a state of uniform motion in a straight line, or remains at rest, |
| |unless acted upon by a resultant force. |
|Newton’s Laws of Motion. 2nd Law |The rate of change of momentum of an object is proportional to the resultant force acting on|
| |it, and takes place in the direction of that force. |
|Newton’s Laws of Motion. 3rd Law |If an object A exerts a force on a second object B, then B must exert a force which is equal|
| |in magnitude but opposite in direction on A. |
|[pic]notation |X is the chemical symbol of the element, A the mass number (number of protons plus number of|
| |neutrons) and Z the atomic number (number of protons). |
|Nucleon. |Protons and neutrons have similar masses. They are both classed as ‘nucleons’. |
|Nuclide |A nuclide is a particular variety of nucleus, that is a nucleus with a particular A and Z. |
|Ohm’s Law. |The current flowing through a metal wire at constant temperature is proportional to the p.d.|
| |across it. |
|Period T for a point describing a|Time taken for one complete circuit. |
|circle. | |
|Period T for an oscillating body |Time taken for one complete cycle. |
|Phase difference |Phase difference is the difference in position of 2 points within a cycle of oscillation |
| |measured as a fraction of the cycle. [Alternatively it can be expressed as an angle where |
| |one whole cycle is 360(] |
|Photoelectric effect |When light or ultraviolet radiation of short enough wavelength falls on a surface, electrons|
| |are emitted from the surface. This is the photoelectric effect. |
|Potential difference (p.d.), V. |The p.d. between two points is the energy converted from electrical potential energy to some|
| |other form per coulomb of charge flowing from one point to the other. |
| |Unit: volt (V) [= JC-1]. |
|Potential energy. |This is energy possessed by virtue of position. (e.g. Gravitational PE = mgh) |
|Power |This is the work done per second, or energy converted or transferred per second. |
| |UNIT: watt (W) [= Js-1]. |
|Radioisotopes |Isotopes (of the same element) have the same atomic number Z but different mass number A. |
| |Radioisotopes are simply isotopes which are radioactive. |
|Relative permeability μr. |When magnetic material of relative permeability μr fills a long solenoid, the magnetic flux |
| |density in the material is given by B = μrB0 where B0 is the flux density when the solenoid |
| |is evacuated. |
|Relative permittivity εr.of an |If capacitance is measured first with vacuum between the plates and then with a slab of |
|insulator or ‘dielectric’ |insulator between, the capacitance increases by a factor εr |
|Resistivity, ρ |The resistance, R, of a metal wire of length L and cross-sectional area A is given by R = ρ |
| |L / A, in which ρ, the resistivity, is a constant (at constant temperature) for the material|
| |of the wire. |
| |Unit: ohm-metre (Ωm) |
|Resonance. |If, in forced vibrations, the frequency of the applied force is equal to the natural |
| |frequency of the system (e.g. mass on spring), the amplitude of the resulting oscillations |
| |is very large. This is resonance. |
|Root mean square value (r.m.s.). |This is a form of average, which is really self defined. Thus for three discrete quantities |
| |1,2 and 3, the r.m.s value is given by [pic]. For sinusoidal variations the r.m.s. value |
| |over a complete cycle is given by the peak (maximum) value divided by [pic]. |
| |(e.g. Irms =IO/[pic]) |
|Scalar |A scalar is a quantity that has magnitude only. |
|Self inductance L. |When a current I through a coil produces a flux linkage NФ, the self inductance of the coil |
|Henry H |is given by L= NФ/I. |
| |Unit: H=WbA-1=Tm2A-1 [= VsA-1] |
|Simple harmonic motion (shm). |Shm occurs when an object moves such that its acceleration is always directed toward a fixed|
| |point and proportional to its distance from the fixed point. (a=-ω2x) |
|Simple harmonic motion (shm). |If the displacement x of a point changes with time t according to the equation x = a |
|(Alternative definition). |sin(ωt+ε) where a, ω and ε are constants, the motion of that point is shm. |
| |[Variations of this kind are said to be sinusoidal because they are determined by a sine |
| |term.] |
|Snell’s law |At the boundary between any two given materials, the ratio of the sine of the angle of |
| |incidence to the sine of the angle of refraction is a constant. |
|Specific heat capacity c. |The heat required, per kilogram, per degree Celsius or Kelvin, to raise the temperature of a|
| |substance. UNIT: J kg-1 K-1 or J kg-1°C-1 |
|Spring Constant |The spring constant is the force per unit extension. |
| |UNIT: Nm-1. |
|Strain |Strain is defined as the extension per unit length due to an applied stress. UNIT: none |
|Stress |Stress is the force per unit cross-sectional area when equal opposing forces act on a body. |
| |UNIT: Pa or Nm-2. |
|Temperature coefficient of |If the resistance of a conductor at 0°C is R0 and its resistance at θ °C is Rθ then α is |
|resistance, α. |defined by: |
| |α = (Rθ – R0 ) / R0θ . [It is the fractional change in resistance per degree rise in |
| |temperature above 0°C.] |
| |Unit: °C-1 |
|Terminal Velocity |The terminal velocity is the constant, maximum velocity of an object when the resistive |
| |forces on it are equal and opposite to the accelerating forces (e.g. pull of gravity). |
|The Law of Conservation of |Electric charge cannot be created or destroyed, (though positive and negative charges can |
|Charge. |neutralize each other). In a purely resistive circuit charge cannot pile up at a point. |
|The moment (or torque) of a |The turning effect of a force (or moment or torque) about a point is defined as the force x |
|force. |the perpendicular distance from the point to the line of action of the force, i.e. moment = |
| |F ( d. |
| |UNIT: Nm. |
|The principle of moments. |For a system to be in equilibrium, ( anticlockwise moments about a point = ( clockwise |
| |moments about the same point. |
|The principle of superposition. |The principle of superposition states that if two or more waves occupy the same region then |
| |the total displacement at any one point is the vector sum of their individual displacements |
| |at that point. |
|The Young Modulus |Young Modulus [pic] |
| |Unless otherwise indicated this is defined for the Hooke’s Law region. UNIT: Nm-2 |
|Thermodynamics. First Law |The heat supplied to a system (e.g. a mass of gas) is equal to the increase in internal |
| |energy plus the work done by the system. (Q = ∆U + W). [The law is essentially a restatement|
| |of the law of conservation of energy including heat as an energy form. Any of the terms in |
| |the equation can be positive or negative, e.g. if 100 J of heat is lost from a system |
| |Q = ( 100 J] |
|Transverse wave |A transverse wave is one where the particle oscillations are at 90( (right angles) to the |
| |direction of travel (or propagation) of the wave. |
|Quantity |Quantity symbol |Unit |Unit symbol |Base unit or equivalent |Scalar(s) or vector(v) |
|Activity | | | | | |
|Amplitude | | | | | |
|Angular velocity | | | | | |
|Area | | | | | |
|Avogadro constant | | | | | |
|Boltzmann constant | | | | | |
|Capacitance | | | | | |
|Charge | | | | | |
|Charge carrier density | | | | | |
|Current | | | | | |
|Decay constant | | | | | |
|Density | | | | | |
|Displacement | | | | | |
|Distance, length, height, width | | | | | |
|Drift velocity | | | | | |
|Electric field strength | | | | | |
|Electric potential | | | | | |
|Electromotive force, EMF | | | | | |
|Energy/work done | | | | | |
|Extension | | | | | |
|Force | | | | | |
|Frequency | | | | | |
|Fringe spacing | | | | | |
|Gravitational field strength | | | | | |
|Gravitational potential | | | | | |
|Impedance | | | | | |
|Intensity | | | | | |
|Internal energy | | | | | |
|Internal resistance | | | | | |
|Magnetic flux | | | | | |
|Magnetic flux density | | | | | |
|Magnetic flux linkage | | | | | |
|Mass | | | | | |
|Molar gas constant | | | | | |
|Moment | | | | | |
|Momentum | | | | | |
|Charge carriers per cubic metre | | | | | |
|Amount of substance | | | | | |
|Number of molecules | | | | | |
|Path difference | | | | | |
|Period | | | | | |
|Permeability of free space | | | | | |
|Permittivity of free space | | | | | |
|Phase | | | | | |
|Planck’s constant | | | | | |
|Plank constant | | | | | |
|Potential difference, voltage | | | | | |
|Power | | | | | |
|Pressure | | | | | |
|Radius | | | | | |
|Reactance | | | | | |
|Refractive index | | | | | |
|Relative molar mass | | | | | |
|Resistance | | | | | |
|Resistivity | | | | | |
|RMS current | | | | | |
|RMS voltage | | | | | |
|Slit width | | | | | |
|Specific heat capacity | | | | | |
|Speed | | | | | |
|Speed of light | | | | | |
|Spring constant | | | | | |
|Stefan-Boltzmann constant | | | | | |
|Stiffness | | | | | |
|Temperature | | | | | |
|Time constant (capacitance) | | | | | |
|Universal constant of gravitation | | | | | |
|Velocity | | | | | |
|(initial, final) | | | | | |
|Volume | | | | | |
|Wavelength | | | | | |
|Weight | | | | | |
|Work function | | | | | |
Further Electromagnetism and Alternating Currents
|Quantity |Quantity symbol |Unit |Unit symbol |Base unit or equivalent |Scalar(s) or vector(v) |
|Reactance | | | | | |
|Impedance | | | | | |
Materials
|Quantity |Quantity symbol |Unit |Unit symbol |Base unit or equivalent |Scalar(s) or vector(v) |
|Strain | | | | | |
|Extension | | | | | |
|Energy density | | | | | |
Biological Measurement and Medical Imaging
|Quantity |Quantity symbol |Unit |Unit symbol |Base unit or equivalent |Scalar(s) or vector(v) |
|Acoustic Impedance | | | | | |
|Absorbed dose | | | | | |
Relationship |Varying quantities |Plot on x-axis |Plot on y-axis |Gradient |y-intercept |Sketch of graph | |[pic] |x & y | | | | | | |[pic] |T & l | | | | | | |[pic] |f & V | | | | | | |[pic] |E & θ | | | | | | |[pic] |R & T | | | | | | |[pic] |x & y | | | | | | |[pic] |x & y | | | | | | |[pic] |f & T | | | | | | |[pic] |V & l | | | | | | |[pic] |Z & f | | | | | | |[pic] |a & g | | | | | | |[pic] |x & y | | | | | | |[pic] |T & m | | | | | | |[pic] |I & n | | | | | | |[pic] |q & t | | | | | | |[pic] |V & t | | | | | | |[pic] |N & t | | | | | | |
-----------------------
Notes for purists:
1. When working at a high academic level, where many repeat measurements are taken, scientists often use “standard error” (, a.k.a. “standard uncertainty”. Where this is used, the expression x0 ± ( is taken to mean that there is a 67% probability that the value of x is in the range x0 ( ( to x0 + (, a 95% probability that it lies in the range x0 ( 2( to x0 + 2(, a 98% probability that it is between x0 ( 3( and x0 + 3(, etc. Our work on uncertainties will not involve this high-level approach.
2. The method which we use here of estimating the uncertainty in an individual quantity takes no account of the number of readings. This is because it is expected that only a small number of readings will be taken. Detailed derivation of standard uncertainties (see above) involves taking the standard deviation of the readings and then dividing this by [pic], so taking 10 readings would involve dividing ( by 3.
3. The above method of combining uncertainties has the merit of simplicity but it is unduly pessimistic. If several quantities are combined, it is unlikely that the actual error (sicl\n\Â\?]6^A^€uuuu$[pic]$[pic]If[pic]gdY?kd¿b $[pic]$[pic]If[pic][?]–l4[pic]Ö[pic][pic][pic][pic][pic][pic]Ö0[?]”ÿpÐ €Ü€`tà[pic][pic]. This is normally done when standard uncertainties are employed (note 1 above).
It is not intended that candidates pursue any of these courses!
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