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Government College University, Faisalabad

Department of Telecommunication Engineering,

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Applied Physics

Lab Manual

Prepared & Edited by:

(Instructors)

Dr. Ijaz Ahmad Khan

(Lab Engineer)

Maria Hanif

Verified by:

Engr. Kashif Nisar Paracha (Lecturer)

Approved by:

Engr. Muhammad Afzal Sipra (TI, M),

Associate Professor, Chairman Telecommunication Engineering

TABLE OF LAB EXPERIMENTS

|Sr. No. |Experiment |Page No. |

| |You will learn how to analyze simple circuits using Ohm’s Law | |

|1. | |6 |

| |You will learn how to determine the frequency of AC supply | |

|2. | |10 |

| |You will learn how to use potentiometer as a voltage divider | |

|3. | |13 |

| |To demonstrate current flow in Rectifier Circuits by using LED’s | |

|4. | |16 |

| |To study the characteristics of RLC series (acceptor) circuit | |

|5. | |21 |

| |To study the characteristics of RLC parallel (rejactor) circuit | |

|6. | |25 |

| |In this experiment you will determine how voltages are distributed in capacitor circuits and explore series and| |

|7. |parallel combinations of capacitors. |29 |

| |To study differentiator & integrator circuits | |

|8. | |33 |

| |You will learn how to use LDR in Circuit design |40 |

|9. | | |

| |To determine the value of an unknown small resistance using a Carey Foster’s bridge |44 |

|10. | | |

| |To determine the height of inaccessible object. |48 |

|11. | | |

|12 |Semester Project |51 |

PREFACE

It is the purpose of the science of Physics to explain natural phenomena. It is in the laboratory where new discoveries are being made. This is where the physicist is making observations for the purpose of identifying the patterns which may later be fit to mathematical equations. Theories are constructed to describe patterns observed and are tested by further experiment.

The laboratory of each and every subject taught in the degree of Bachelors in Electrical Engineering is of very much importance in every University. Fully equipped laboratory meeting the industrial demands under the supervision of qualified, talented and practically motivated lab assistants and lab engineers is also a basic criterion of the Pakistan Engineering Council. This Manual has been formulated considering all these above mentioned points.

This manual is according to the equipment supplied by the RIMS, USA and meets the requirements of all the course of Applied Physics as per the curriculum of G. C. University Faisalabad.

Special thanks to the following staff and students for assisting me in the preparation of this manual.

With Regards

Dr. Ijaz Ahmad Khan.

General Lab Instructions:

➢ Each student group consists of a maximum of 2-4 students. Each group member is responsible in submitting lab report upon completion of each experiment on their practical Note book.

➢ Students are to wear proper attire i.e. shoe or sandal instead of slipper. Excessive jewelleries are not advisable as they might cause electrical shock.

➢ A permanent record in ink of observations as well as results should be maintained by each student and enclosed with the report.

➢ The recorded data and observations from the lab manual need to be approved and signed by the lab instructor upon completion of each experiment.

➢ Before beginning connecting up, it is essential to check that all sources of supply at the bench are switched off.

➢ Start connecting up the experiment circuit by wiring up the main circuit path, then adds the parallel branches as indicated in the circuit diagram.

➢ After the circuit has been connected correctly, remove all unused leads from the experiment area, set the voltage supplies at the minimum value, and check the meters are set for the intended mode of operation.

➢ The students may ask the lab instructor to check the correctness of their circuit before switching on.

➢ When the experiment has been satisfactory completed and the results approved by the instructor, the students may disconnect the circuit and return the components and instruments to the locker tidily. Chairs are to be slid in properly.

Experiment No. 1

VERIFICATION OF OHM’S LAW

OBJECTIVE:

• In this lab you will learn how to analyze simple circuits using Ohm’s Law

EQUIPMENT:

• Digital Multimeter (DMM)

• Resistors:

• E-PAL (Training board)

THEORY:

Ohm's law states that the current through a conductor is directly proportional to the potential difference across the ends of the conductor.

[pic]

Fig.1 Ohm’s law

Mathematically

V = IR

where I is the current (amperes), V is the potential difference (volts) and R is the resistance of the conductor (ohms). If, R is constant than there is a linear relation between V and I.

The law was named after the German physicist Georg Ohm,

The slope of a V(I) graph is R. This relationship can be checked by measuring the current through and voltage across each resistor.

When measuring current be sure to place the ammeter in series with the components in question. Current flows through a circuit. When measuring voltage be sure to place the voltmeter in parallel with the resistance. Voltage drops across a resistor.

No doubt you noticed in the DC Circuits lab that voltages recorded across the series components very nearly summed to the power supply voltage. And it's almost certain that you discovered that voltage measured across each component in the parallel configuration was quite close to the power supply setting. Therefore, your astute observations should help you with this experiment as well.

PROCEDURE:

Set the circuits below. Please be careful when you setup the input voltage.

Circuit 1 (Series)

1. Construct this circuit below.

2. Let R1 = 180 Ohms, R2 = 220 Ohms, R3 = 330 Ohms

3. Set the power supply to 12 volts.

4. Measure the current (in milliamps) through and voltage drop (in volts) across each resistor.

CIRCUIT DIAGRAM:

Fig.2 Resisters in series

Circuit 2 (Parallel)

1. Construct the circuit below.

2. Let R1 = 180 Ohms, R2 = 220 Ohms, R3 = 330 Ohms.

3. Set the power supply to 3 volts.

4. Measure the current (in milliamps) through and voltage drop (in volts) across each resistor.

5. Also measure the current between the + side of the battery or power supply and R1.

CIRCUIT DIAGRAM:

Fig.3 Resister in parallel combination

CALCULATIONS:

For circuit # 1 (series):

1. Calculate the total resistance.

2. Calculate the theoretical current (in Amps) value using the total resistance value and the value of the input voltage.

3. Calculate the theoretical value of the voltage drop across each resistor by using the theoretical current value.

4. Calculate the percent error for the current (use the average of your measured values (in Amps) as your experimental value).

5. Calculate the percent error for the voltage drops across each resistor.

For Circuit # 2 (parallel):

1. Calculate the total resistance.

2. Calculate the theoretical value of the total current (in Amps) by using the total resistance and the value of the input voltage.

3. Calculate the theoretical value of the current (in Amps) through each resistor. You may assume that the voltage across each resistor is the same as the input voltage.

4. Calculate the percent error for the total current.

5. Calculate the percent error for the values of the currents through each resistor.

RESULTS & CALCULATIONS:

For circuit # 1:

RT (calculated) = ___________,

I(calculated) using calculated value of RT and input voltage V= ___________

VR1 (calculated) = ___________, VR2(calculated) = ___________

VR3 (calculated) = ___________

For circuit # 2:

RT (calculated) = ___________,

I(calculated) using calculated value of RT and input voltage V= ___________

IR1 (calculated) = ___________, IR2(calculated) = ___________

IR3 (calculated) = ___________

DISCUSSION AND CONCLUSION:

1) -------------------------------------------------------------------------------------------

2) -------------------------------------------------------------------------------------------

3) --------------------------------------------------------------------------------------------

Experiment No. 2

MELDE’S EXPERIMENT

OBJECTIVE:

In this lab you will learn how to determine the frequency of AC supply.

EQUIPMENT:

• A stand with clamp and pulley  

• A light weight pan  

• A weight box

•   Balance 

•  A battery with eliminator and connecting wires  

[pic]

Fig.1 Melde's experiment

THEORY:

“ An experiment to study transverse vibrations in a long, horizontal thread when one end of the thread is attached to a point of a vibrator , while the other passes over a pulley and has weights suspended from it to control the tension in the thread. “

Melde's experiment is a scientific experiment carried out by the German physicist Franz Melde on the standing waves produced in a tense cable originally set oscillating by a tuning fork, later improved with connection to an electric vibrator. This experiment attempted to demonstrate that mechanical waves undergo interference phenomena. In the experiment, mechanical waves traveled in opposite directions from immobile points, called nodes. These waves were called standing waves by Melde since the position of the nodes and loops (points where the cord vibrated) stayed static.

Transverse wave motion:

 A transverse wave motion is that wave motion, in which individual particles of the medium execute simple harmonic motion about their mean position in a direction perpendicular to the direction of propagation of wave motion.

Fig.2 Transverse wave

Tension:

In physics, tension is (magnitude of) the pulling force exerted by a string, cable, chain, or similar solid object on another object.

PROCEDURE:

1) Find the weight of pan and mass of thread 1cm in length.

2) Set the apparatus according to figure.

3) Excide the steel strip by passing A.C. current through the coil of electromagnet and put a small weight in the scale pan. The thread will vibrates under the forced vibration of steel strip.

4) Take the readings according to table and calculate the frequency by using this formula:

n=1/2l(√T/m)

5) Increase the weights in pan and calculate the frequency again.

[pic]

Fig.3 Block diagram of melde’s experiment

RESULTS & CALCULATIONS:

Table 1

|No. of Obs. |Mass of |No. of loops |Distance |Length of |Mass of the |Tension in |n=1/2l√(T/m) |

| |weight in pan|p |between |each loop |pan+ wts. |dynes T=Wx981| |

| | | |extreme nodes |l=L/p |Added to it | | |

| | | |L | |W | | |

|  |gms |  |cms. |cms. |gms |dynes |vib./sec. |

|1 |  |  |  |  |  |  |  |

|2 |  |  |  |  |  |  |  |

|3 |  |  |  |  |  |  |  |

|4 |  |  |  |  |  |  |  |

DISCUSSION AND CONCLUSION:

1. -------------------------------------------------------------------------------------------

2. -------------------------------------------------------------------------------------------

3. --------------------------------------------------------------------------------------------

Experiment No.3

TO STUDY POTENTIAL DIVIDER CIRCUIT

OBJECTIVE:

In this lab you will learn how to use potentiometer as a voltage divider.

EQUIPMENT / COMPONENTS REQUIRED:

• DMM

• TRAINER BOARD

• Resistor

• Variable resistor

LAB SAFETY CONCERNS:

• Make sure all circuit connections are correct, and no shorted wires exist.

• Adjust the power supply to the proper voltage before connecting it to the circuit

• Adjust signal generator to the proper level before connecting it to the circuit

• When using electrolytic capacitors, the arrows must point to the negative side of current flow.

THEORY:

A potentiometer is a manually adjustable electrical resistor that uses three terminals. In many electrical devices, potentiometers are what establish the levels of output. For example, in a loudspeaker, a potentiometer is used to adjust the volume. In a television set, computer monitor or light dimmer, it can be used to control the brightness of the screen or light bulb.

Fig.1 Potentiometer

Fig.2 Circuit diagram of potentiometer

Working:

Potentiometers, sometimes called pots, are relatively simple devices. One terminal of the potentiometer is connected to a power source, and another is hooked up to a ground — a point with no voltage or resistance and which serves as a neutral reference point. The third terminal slides across a strip of resistive material. This resistive strip generally has a low resistance at one end, and its resistance gradually increases to a maximum resistance at the other end. The third terminal serves as the connection between the power source and ground, and it usually is operated by the user through the use of a knob or lever.

The user can adjust the position of the third terminal along the resistive strip to manually increase or decrease resistance. The amount of resistance determines how much current flows through a circuit. When used to regulate current, the potentiometer is limited by the maximum resistivity of the strip.

Fig.3 Circuitry of variable resistor

PROCEDURE:

Construct the circuit given in figure below

Fig.4Circuit diagram

CALCULATIONS

1) Calculate & Measure the value of Vout.

2) What happens if 9k is replaced by 1k?

3) What happens if 9k is replaced with 2k?

4) What happens if 1k is replaced with zero?

5) .Replace +12V with ground. Measure Vout and answer all of the above questions.

CONCLUSION:

1. ---------------------------------------------------------------------------------------------------

2. ---------------------------------------------------------------------------------------------------

3. ---------------------------------------------------------------------------------------------------

Experiment No. 4

RECTIFIER CIRCUIT

OBJECTIVE:

To demonstrate current flow in Rectifier Circuits by using LED’s

EQUIPMENT / COMPONENTS REQUIRED:

• DMM

• Trainer Board

• Resistor

• Diode

THEORY:

Half-Wave Rectifiers

An easy way to convert ac to pulsating dc is, to simply allow half of the ac cycle to pass, while blocking current to prevent it from flowing during the other half cycle. The figure below shows the resulting output. Such circuits are known as half-wave rectifiers because they only work on half of the incoming ac wave. 

[pic]

Fig.1 Half Wave Rectifier

[pic]

Fig.2 Output of Half wave rectifier

Full-Wave Rectifiers

The more common approach is to manipulate the incoming ac wave so that both halves are used to cause output current to flow in the same direction. The resulting waveform is shown below. Because these circuits operate on the entire incoming ac wave, they are known as full-wave rectifiers  

Fig.3 Full-Wave Rectifier

Fig.4 output of Full wave rectifier

PROCEDURE:

For half wave rectification

• Construct the circuit given in figure below.

• Observe the out put using oscilloscope.

• Make the following measurements and take the snap short of out put signal.

.

Fig.5 Circuit Diagram

CALCULATIONS

Table 1

|Sr. no. |In put |Out put |

|  |(Vrms) |(V)  |

|1 |20 |  |

|2 |30 |  |

GRAPH

For full-wave rectification

• Construct the circuit given in figure below.

[pic]

Fig.6 Circuit Diagram

• Observe the out put using oscilloscope.

• Make the following measurements and take the snap short of out put signal.

Table 2

|Sr. no. |In put |Out put |

|  |Vrms | V |

|1 |20 |  |

|2 |30 |  |

GRAPH

CONCLUSION:

1. ------------------------------------------------------------------------------------------------------------

2. ------------------------------------------------------------------------------------------------------------

3. ------------------------------------------------------------------------------------------------------------

Experiment No. 5

ACCEPTOR CIRCUITS

OBJECTIVE:

• To study the characteristics of RLC series (acceptor) circuit

EQUIPMENT / COMPONENTS REQUIRED:

• Audio oscillator

• Resistors (100-1000 ohm)

• Capacitors (0.1µf)

• Inductance (500mH)

• DMM

THEORY:

A given combination of R, L and C in series allows the current to flow in certain frequency ranges only. For this reason it is known as an acceptor circuit i.e., it accepts some specific frequencies.

A series-resonant circuit that has a low impedance at the frequency to which it is tuned and a higher impedance at all other frequencies

At resonance frequency, XC=XL and XL-XC = 0. Therefore, the only electrical characteristic left in the circuit to oppose current is the internal resistance of the two components and resistance used. Hence, at resonance frequency, Z = R.

RESONANCE:

For a certain frequency of the sinusoidal voltage applied to RLC series circuit the current flowing in the circuit has a maximum value. This phenomenon is called resonance.

[pic]

RESPONSE CURVE:

When RLC series circuit is excited by a sinusoidal voltage, the current changes with frequency of applied voltage. A graph between current n frequencies is known as the response curve.

[pic]

Fig.1 Response curve

QUALITY FECTOR:

It is the ratio between the resonance frequency and the bandwidth, i.e.

Quality factor=Q= fr/∆f

PROCEDURE:

• Construct the circuit given in figure below.

Fig.2 Circuit diagram

• Set the oscillator to resonance frequency.

• Switch on the oscillator and observe the current flowing in the circuit with the help of multi-meter.

• Observe the current by increasing and decreasing the frequency and note the corresponding current.

• Record two more sets of observations for different values of R.

GRAPH:

CALCULATIONS:

[pic]

fr=………hertz

|R ohms |No. of Obs. |1 |2 |3 |

|1 |  |  |  |  |

|2 |  |  |  |  |

|3 |  |  |  |  |

|4 |  |  |  |  |

|5 |  |  |  |  |

Voltage change= Vout in shade – Vout in light

CIRCUIT DIAGRAM No. 1:

[pic]

Fig.1 Circuit diagram

CONCLUSION:

1. With this circuit, is Vout HIGH or LOW in the light?

2. Which test resistor gives the biggest voltage change between light and shade?

3. Which resistor would you use to make your light sensor most sensitive to changes in illumination?

4. Repeat the procedure by changing the position of LDR and fixed resistor.

5. Now take Vout across the LDR

CIRCUIT DIAGRAM 2:

[pic]

Fig.2 Circuit diagram

Table 2

|No. of Obs. |Fixed resistor value |Vout in the light |Vout in the shade |Voltage change |

|1 |  |  |  |  |

|2 |  |  |  |  |

|3 |  |  |  |  |

|4 |  |  |  |  |

|5 |  |  |  |  |

CONCLUSION:

1. With the second circuit, is Vout HIGH or LOW in the light?

2. Which test resistor gives the biggest voltage change between light and shade?

3. Which resistor would you use to make your light sensor most sensitive to changes in illumination?

Experiment No. 10

CAREY FOSTER’S BRIDGE

OBJECTIVE:

To determine the value of an unknown small resistance using a Carey Foster’s bridge

EQUIPMENT:

• An unknown resistance

• A known resistance(variable)

• A DMM

• A dry cell

• A plug key

• A meter bridge with jockey

• A sorting plate

• A copper strip

THEORY:

The Carey Foster bridge is an electrical circuit that can be used to measure very small resistances. It works on the same principle as Wheatstone’s bridge, which consists of four resistances, P, Q, R and S that are connected to each other as shown in the circuit diagram below. In this circuit, G is a galvanometer, E is a lead accumulator, and K1 and K are the galvanometer key and the battery key respectively. If the values of the resistances are adjusted so that no current flows through the galvanometer, then if any three of the resistances P, Q, R and S are known, the fourth unknown resistance can be determined by using the relationship

P/ Q= R/S

[pic]

Fig.1 Wheatstone’s bridge

PROCEDURE:

The connections are made as shown in fig.2 such that potential divider acts as two equal resistances P & Q. Now connect the copper strip in right gap of the bridge and a known resistances (R) in the left gap. The null point is determined and it’s distance l′1 from the bridge is measured. Interchange the position of R and copper strip and note the distance l′2 of the new null point from the left end. Take at least three readings for different values of known resistances.

Now the given wire whose resistance is to be determined (say Y) is placed in the right gap in place of copper strip and known resistance in left gap (X).Find the null point and the distance l1 and similarly l2 when X & Y are interchanged. Take at least three readings for different values of Y.

[pic]

Fig.2Block diagram Wheatstone’s bridge

CALCULATIONS:

FORMULAS USED

For unknown resistance Y:

Y=X-ρ(l2-l1)Ω

Where X is the resistance introduced in the resistance box

l1 is the length of the balance point in the bridge wire where resistance box is in the left gap

l2 is the length of the balance point in the bridge wire where resistance box is in the right gap

The resistance per unit length (ρ )of the bridge wire is determined by:

ρ= R/( l′2-l′1) ohm/cm

Where R is the known resistance in the resistance box.

Table 1For determination of ρ

|Sr. No. |R |Distance of the null point |Shift in balance point | ρ= R/( l′2-l′1) |

| | |When X in left gap |When X in left gap |l′2-l′1 |  |

|  |ohm |l′1 (cm) |l′2(cm) |cm |ohm/cm |

|1 |  |  |  |  |  |

|2 |  |  |  |  |  |

|3 |  |  |  |  |  |

|4 |  |  |  |  |  |

|5 |  |  |  |  |  |

Table 2 For determination of X

|Sr. No. |X |Distance of the null point |Shift in balance point | Y=X- ( l2-l1) |

| | |When Y in left gap |When Yin left gap |l2-l1 |  |

|  |ohm |l1 (cm) |l2(cm) |cm |ohm/cm |

|1 |  |  |  |  |  |

|2 |  |  |  |  |  |

|3 |  |  |  |  |  |

|4 |  |  |  |  |  |

|5 |  |  |  |  |  |

CONCLUSION:

1) What is the principle of Wheatstone bridge?

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2) What is the principle of Carey Foster’s bridge bridge?

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3) When is the C.F. bridge most sensitive?

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Experiment No. 11

SEXTANT

OBJECTIVE

• To determine the height of inaccessible object.

EQUIPMENT:

• Sextant

• Rigid stand with clamp

• Measuring tape

• Plump line spirit level

• Colored chalks

THEORY

A sextant is an instrument used to indirectly measure distances. A measuring tape or meter stick is incapable of measuring the distance to a star. Sextants have been used for centuries to make this sort of indirect measurement. In this activity sextants will be made and used to measure the height of a very tall object, such as a flagpole or a building.

Fig.1 Sextant

PROCEDURE

1. Choose an observation point from which you can clearly see both the top and the bottom of the object you wish to measure. Determine the exact distance between the observation point and the base of the object.

2. Set the sextant to zero and look at the object through the eyepiece, adjusting your view until it is in the center of the frame.

3. Adjust the sextant arm to split the screen in two halves. Continue moving the arm until the top half of the object on one side of the image is aligned with the bottom half of the object on the other side of the image.

4. Use a scientific calculator to find the height of the object by multiplying its distance from the observation point by the tan of the angle that you measured. For example, if you were 150 feet from the base of the object, and the recorded angle was 75 degrees, the height of the object would be 150 x tan 75 = 560 feet.

OBSERVATIONS & CALCULATIONS

• Vernier constant of the sextant =…………

• Initial reading of the vernier against

SS for the two mirrors parallel =…………

• Zero correction =…………..

• Height of the mark Q above the

ground =……........

Table 1

|Sr. No. |Sextant at point R |Sextant at point S |Horizontal distance |Vertical distance |

| | | |between the points R|between the top and |

| | | |& S (d) |reference mark Q |

| | | | |h=d/(cotθ2 -cotθ1) |

|Initial reading

A |Final reading

B |Angle θ1=B-A |Initial reading C |Final reading D |Angle θ2=D-C | | | |1 |  |  |  |  |  |  |  |  | |2 |  |  |  |  |  |  |  |  | |3 |  |  |  |  |  |  |  |  | |

DISCUSSION AND CONCLUSION

1) -------------------------------------------------------------------------------------------

2) -------------------------------------------------------------------------------------------

3) --------------------------------------------------------------------------------------------

(SEMESTER PROJECT)

ELECTRIC MOTOR

OBJECTIVE:

• The objective of this project is to build a simple electric motor in order to explore the inter-relationship of electricity & magnetism.

THEORY:

An electric motor is an electromechanical device that converts electrical energy into mechanical energy.

Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force. The reverse process, producing electrical energy from mechanical energy, is done by generators such as an alternator or a dynamo; some electric motors can also be used as generators, for example, a traction motor on a vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines.

USES:

Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives.

OPERATING PRINCIPLE:

Nearly all electric motors are based around magnetism (exceptions include piezoelectric motors and ultrasonic motors). In these motors, magnetic fields are formed in both the rotor and the stator. The product between these two fields gives rise to a force, and thus a torque on the motor shaft. One, or both, of these fields must be made to change with the rotation of the motor. This is done by switching the poles on and off at the right time, or varying the strength of the pole.

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