GOVERNMENT ENGINEERING COLLEGE B M ROAD, HASSAN DEPARTMENT OF PHYSICS

Transcription

1 E=kT GOVERNMENT ENGINEERING COLLEGE Name of the Student : USN : Branch : B M ROAD, HASSAN DEPARTMENT OF PHYSICS PREPARED BY N R SREENATHA. MSc.,MPhil.,B.Ed. Assistant Professor & Head Department of Physics Government Engineering College B.M. Road Hassan NH PREPARED BY N R SREENATHA M.Sc.,B.Ed.,M.Phil. Assistant Professor & Head Deoartment Of Physics Government Engineering College Hassan Page 1

2 INSTRUCTIONS FOR STUDENTS 1. Bring the observation book and practical manual for each practical class. 2. Read the experiment at least once or twice before coming to the practical class the experiment which you have to perform. 3. The experiment that you have performed in the lab, same has to be discussed with your friends after finishing your lab. 4. You are asked to bring the necessary stationeries (pen, pencil, calculator, eraser etc.,) for each practical class. 5. Draw the relevant tabular column and the formula/formulae of the experiment in the observation book in advance before coming to the practical class. 6. You are asked to show the observation book to the lab in charge teacher after the completion of the experiment, same has to be written in the practical record before attending the next practical class. 7. You are strictly warned not to bring mobile phones and any other disturbing electronic gadgets to the class. 8. You are asked to return the lab apparatus which are collected after the completion of your experiment. 9. You are informed to handle the apparatus with utmost care. 10. If we noticed that you are damaged any apparatus for that the equivalent amount will be charged immediately. 11. You are not permitted to leave the lab between the lab hours. 12. Don t switch on electronic equipment before getting the approval of the teacher. Page 2

3 CONTENT S.NO. NAME OF THE EXPERIMENT PAGE NO. 1. Planck s constant Stefan s constant 07 Page 3 3. Transistor characteristics Zener diode characteristics Determination of dielectric constant Diffraction Laser Verification of parallel resonance using LCR circuit Verification of series resonances using LCR circuit B-H curve (transformer core) B-H curve (ferrite core) 33

4 CIRCUIT DIAGRAM TO DETERMINE PLANCK S CONSTANT R + ma _ Page V Ba LED OBSERVATION c - Speed of light in air = 3 X 108 m/s e Charge of an electron = 1.6 X 10-19C TABULATION TO DETERMINE PLANCK S CONSTANT Planck s constant TRIAL No. 1 Color of LED Glow on Voltage V in volt Green Wavelength λ in nm Yellow Blue Red h= in JS CALCULATION PART To calculate Planck s constant: h= in Js Where e charge of an electron c Speed of light in air v Glow on voltage for LED color λ Wavelength of LED color = = = =

5 PLANCK S CONSTANT EXPERIMENT NO: DATE: AIM: Determination of Planck s constant using LED s of different colors, also calculate the energy gap for any LED in electron volt. APPARATUS: LED s and Planck s constant kit. Page 5 THEORY: The LED is the heavily doped pn junction which emits light when it is in forward bias, when the electron in the conduction band recombines with holes in the valence band and difference in energy emits in the form of light. LED converts electrical into light energy, Plank s law states that the radiation emitted or absorbed by the body is not a continuous one but takes place in the form of discrete packets, energy of the each packet is given by E=hυ E2-E1=Eg = hυ ev= h FORMULA: Planck s constant h= in Js Where e Charge of an electron in coulomb. c Speed of light in air = 3x108ms-1 V Glow on voltage in volt. λ Wavelength of LED color in metre. PROCEDURE: 1. Electrical connections are made as shown in figure. 2. Connect the LED to the jack provided on the front panel and switch ON the unit. 3. The voltage applied across the LED using TTP is increased gradually from zero and the readings of the voltmeter is noted when the LED just glows. This voltage is called glow on voltage or knee voltage (V). 4. The experiment is repeated for different colors of LED s and the readings of voltmeter are noted in each case. 5. Readings are tabulated. 6. Planck s constant can be calculated using the above formula for various colors and average value of h is obtained. RESULT Planck s constant h=.. Js

6 CIRCUIT DIAGRAM TO DETERMINE STEFAN S CONSTANT ma _ + Page Ba Black Body V - OBSERVATION: Room temperature T = = K TABULATION TO DETERMINE STEFAN S CONSTANT: Trial.No. Voltage V in volt Current I in ma Steady temperature of the black body T in K Stefan s constant σ = in W/m2/K4 CALCULATION PART TO CALCULATE STEFAN S CONSTANT σ= in W/m2/K4 V Potential difference across the black plates I Current through black plates T- Steady Temperature of black plates To- Room temperature A- Area of the black plates =..in volt =..in ma =..ink =. ink =312.2x10-4m2

7 STEFAN S CONSTANT EXPERIMENT NO: DATE: AIM: To determine Stefan s constant. APPARATUS: Stefan s constant kit, black body (metallic plates), thermometer etc. THEORY: The body is one which neither reflects nor transmits but completely absorbs is known as black Page 7 body and emits same when it is heated. Stefan s law states that energy emitted or absorbed by the black body per unit area in one second is directly proportional to the fourth power of its absolute temperature. E α T4 E = σ T4 =σ Temperature of the black plates increases and becomes steady state when the fixed voltage applied across it; at the steady state the electrical energy consumed by the black plates becomes equal to the heat energy radiated by the black plates. FORMULA To calculate Stefan s constant σ= in W/m2/K4 Where V- Voltage applied across the black plates in volt I current through the black plates in ma T- Steady temperature of the black body in K T0- Room temperature in K A Area of the black body (plates) in sq.metre. PROCEDURE: 1. Note down the room temperature using thermometer. 2. Place the discs horizontally on the wooden table. 3. Connect the heating element of discs to the kit terminals marked as Black Plates. 4. Adjust the potential difference (V) with the help of potentiometer and the current (I) for heating element for proper readings in the meters. 5. Place the thermometer vertically in the holder provided on top of the discs. 6. Observe the readings of the thermometer till the temperature of the black body becomes steady (constant) and steady temperature is noted. 7. Experiment is repeated for different voltages and steady temperature is recorded in each case and the readings are tabulated. 8. Stefan s constant can be calculated using the above mentioned formula. RESULT Stefan s Constant is σ = in W/m2/K4

8 CIRCUIT DIAGRAM FOR STUDYING TRANSISTOR CHARACTERISTICS IC C A - IB + + ma - + Page B + -VBB E VCE - Vcc -VBE TABULATION TO STUDY INTPUT CHARACTERISTICS OF A TANSISTOR Set VCE = 4 volt VBE in volt IB in µa IB in µa ΔI ΔV VBE in volt Note: Triangle form should be small & it should taken in the linear portion of the curve

9 TRANSISTOR CHARACTERISTICS EXPERIMENT NO: DATE: AIM: To study the input, output and transfer characteristics of an N-P-N transistor in the common emitter mode and also determining the input resistance (Ri), output resistance (Ro)and the current gain (β) of the given transistor. APPARATUS: Given transistor (npn), variable DC power supplies (0-2V&0-20V) DC micro ammeter (0-200µA), DC milli ammeter (0-20 ma), DC voltmeter (0-2V&0-20V), connecting wires [All devices are inbuilt on the experiment box] FORMULA: in Ω 1) Input resistance Where, ΔVBE = Small increment in the base emitter voltage in volt ΔIB = Small increment in the base current in µa in Ω 2) Output resistance ΔVCE = Small increment in the collector emitter voltage in volt ΔIC = Small increment in the collector current in ma 3) Current gain no unit PROCEDURE: The common emitter circuit for studying the transistor characteristics of an npn transistor is shown in fig. First identify the terminals of different devices required for the experiment on the experimental box. Give the connections using connecting wires carefully according to the circuit diagram. Before switching on the circuit, verify once again the circuit connections. Now turn all power supply knobs to the minimum position & switch on the power supply. Check that circuit is working properly. INPUT CHARACTERISTICS 1. To study the input characteristics of the transistor first turn all power supply knobs to minimum position. Now collector-emitter voltage VCE is set to 4 volt by varying Vcc(supply-2). Keeping VCE = 4 volt as constant, increase the values Base-Emitter voltage VBE by turning VBB(supply-1) & note down the corresponding values Base current IB in microammeter. Readings are tabulated. A graph of VBE values along X- axis & IB values along Y- axis is plotted. Calculate the input resistance using the above formula (Ri). The study of variation of input current with the variation input voltage is called input characteristics of a transistor. Page 9

10 TABULATION TO STUDY OUTPUT CHARACTERISTICS OF A TANSISTOR Set IB = 30 A VCE In volt 0.00 IC In ma Page 10 Ic In ma VCE (volts) Note: Triangle form should be small & it should be taken in the linear portion of the curve TABULATION TO STUDY TRANSFER CHARACTERISTICS OF A TRANSISTOR Set VCE =10 volt IB in A 0.00 IC in ma Ic (ma) IB ( A)

11 OUTPUT CHARACTERISTICS (Ro): 1. To study the output characteristics of the transistor, once again turn all the power supply knobs to minimum position. 2. The Base current IB is set to 30 μa by turning VBB knob. 3. Keeping IB =30 μa as constant, apply different values of collector-emitter voltage VCE and Page 11 note down corresponding values of collector current Ic in milli amperes. 4. Begin VCE values as from 0.0, 0.2, 0.4, 0.6, 0.8 volts till 1.00 volt. 5. After VCE = l.00 volt, increase the VCE values in steps of l volt ( say 2.0, 3.0, 4.0, 5.0,) and note the corresponding collector Ic for each VCE voltage applied. 6. Tabulate all the readings in relevant tabular column for output characteristics. (Note: Care should be taken that while taking each reading of Ic, IB should read the constant values i.e. IB =30 μa). 7. Tabulate all the readings properly. 8. A graph of VCE along X-axis and Ic along Y-axis is plotted and output resistance can be calculated (Ro). 9. The study of the variation of output current with the variation of output voltage is called as output characteristics of a transistor. CURRENT TRANSFER CHARACTERISTICS(β): To study the Transfer characteristics of the transistor. Turn all the power supply knobs to minimum position again. Set the collector-emitter voltage once againvce for 10 volt. Apply different values of Base current (say IB = 0.00 μa, 20 μa, 40 μa, 60 μa, 80 μa, & l00 μa) and record the corresponding values of collector current Ic in milli amperes each time. Tabulate the readings in relevant tabular column for transfer characteristics. A graph of IB along X-axis & Ic along Y-axis is plotted. The graph obtained will be a straight line, calculate the slope and slope will be the ratio ΔIC / ΔIB, which is equivalent to current gain β. The study of variation of output voltage with the variation of input voltage called current transfer characteristics of a transistor. The current flows from low resistance forward bias to the high resistance reverse bias hence it is named as current transfer characteristics. RESULT: 1. The input resistance = 2. The output resistance = 3. Current gain factor = Ri = Ω Ro = Ω β = no unit

12 CIRCUIT DIAGRAM FOR ZENER DIODE CHARACTERISTICS FORWARD BIAS CHARACTERISTICS R ma V Ba (0-20V) Zener Diode REVERSE BIAS CHARACTERISTICS R µa - + _ + - Ba(0-20V) _ V Zener Diode SPECIMEN GRAPH I F + + Forward voltage V F in volt Reverse voltage V R in volt Forward current I F in ma Page 12 Reverse current I R in µa V RB V F V R 0 knee voltage I R

13 ZENER DIODE CHARACTERISTICS EXPERIMENT NO: DATE: AIM: To study the IV characteristics of a given Zener diode, and hence to determine the knee voltage and Zener break down voltage. APPARATUS: Zener diode (5.1V/7.5V), 0 to 20V voltage power supply, digital voltmeter, digital ammeter (milli ammeter & micro ammeter), etc. [All the devices are inbuilt in a Zener diode kit]. THEORY: The Zener diode is the heavily doped pn junction works under reverse bias, at the particular forward bias voltage the current increases sharply. FORMULA: Forward resistance in Ω Where = small change in forward voltage in volt = small change in forward current in ma PROCEDURE: 1. FORWARD BIAS CHARACTERISTICS 1. The circuit for studying the forward bias characteristics of a Zener diode is as shown in circuit diagram. 2. Identify the terminals of Zener diode. Observe the black colored circular ring on one side of Zener diode, it is negative terminal (n-type) of Zener diode and the other side is p-type. 3. Connect positive terminal to positive end of circuit and negative terminal to negative end then it is said to be forward bias. 4. ammeter is connected to digital milli ammeter 5. Turn all the knobs to minimum position before switching on the power supply. 6. Apply voltage in steps of 0.1, 0.2, 0.3V etc, till the DCM (Digital Current Meter) reads a proper value of current. 7. Generally for a Zener diode (7V) till 0.6V DCM reads zero current. Hence 0.6V onwards the voltage must be increased in steps of 0.01V till 0.8V and the corresponding DCM readings in milli amperes are noted. 8. Tabulate the readings. 2. REVERSE BIAS CHARACTERISTICS 1. The circuit for studying the reverse bias characteristics is as shown in circuit diagram. 2. Modify forward bias circuit into reverse bias circuit as said in below. 3. First interchange the terminals of Zener diode, and second is switch over the DCM from milli ammeter to micro ammeter. 4. Now using the power supply knob of 0 to 20V, apply voltage values as lv, 2V, 3V... till the micro ammeter (DCM) reads some large current i.e., Zener diode reaches the breakdown point. 5. Near breakdown region give very small increments of order 0.01V and note down the corresponding DCM readings. 6. Take at least ten/twelve readings. 7. Tabulate all the readings in the relevant tabular column. 8. The reverse voltage at which the Zener break down takes place is called break down voltage. Page 13

14 3. GRAPHS: 1. To plot the I-V characteristics graphs, take a suitable graph sheet divided into four quadrants. 2. In the first quadrant choosing appropriate scale plot the characteristics of forward bias mode. 3. In the third quadrant Plot the I-V characteristics for reverse bias mode choosing appropriate scale. Page The graph looks as one shown in specimen graph. 5. To determine the forward bias knee voltage, draw a tangent at the knee portion of forward characteristics curve. The voltage corresponding to point where the tangent touches the xaxis is called forward knee voltage. 6. To determine break down voltage in reverse characteristics, identify a stage after which the reverse current rises steeply. The voltage corresponding to that stage on negative x-axis is called reverse breakdown voltage; it is a characteristic for a particular Zener diode. 7. The forward resistance can be calculated using the above formula. RESULT: The value of forward knee voltage VK = in volt The value of reverse breakdown voltage VRB = in volt The forward resistance is RF = in ohm Note: The scale for plotting forward bias characteristics & reverse bias characteristics will Be different

15 CIRCUIT DIAGRAM FOR CHARGING & DISCHARGING OF A CAPACITOR R output + ma - R 2 X Page 15 R 3 Y BLANK + INPUT CHARGE DISCHARGE C 1 C 2 C 3 DUMP ON V _ - - output TABULATION FOR CHARGING AND DISCHARGING OF A CAPACITOR S. NO. Time T In sec Voltage across the capacitor V In volt SPECIMEN GRAPH Charging curve V In volts 0 t = T 1/2 time in second Discharging curve

16 DETERMINATION OF DIELECTRIC CONSTANT BY CHARGING AND DISCHARGING OF A CAPACITOR EXPERIMENT NO: DATE: AIM: Determination of dielectric constant (K) of the given material by the method of charging and discharging of a given capacitor. Page 16 APPARATUS: Capacitor, Resistor, Two way toggle switch, Voltmeter [are all inbuilt in the experimental box] and stopwatch. FORMUIA: Dielectric constant of a given material is given by no unit Where, K = Dielectric constant of the given dielectric material no unit. T½ = Time taken by the capacitor for half charging or discharging ( Vmax/2) ε0 = Permittivity of free space = x F/ m R = Resistance used in the experiment in ohm. PROCEDURE CHARGING MODE 1. Construct the circuit as shown in the circuit diagram & switch ON the unit. 2. Initially set the current to 0.5mA by keeping toggle switch towards charge position and dump switch towards ON position. 3. The capacitor is allowed to charge by putting the dump switch towards blank position. 4. The voltage across the capacitor is recorded at an interval of 5 second using a stopwatch, until V becomes practically constant and the readings are tabulated. [i.e., when two consecutive readings remain same] DISCHARGING MODE The following operation has to be performed in quick successions. 1. Now the stop watch is reset, the capacitor is allowed to discharge by the toggle switch is changed towards discharge position and simultaneously stopwatch is started, the voltage across the capacitor once again is recorded until the V becomes practically zero for the same interval of time. DETERMINATION OF TIME CONSTANT [T½] THROUGH THE GRAPH 1. A graph of time[t] along X-axis, and voltage V along Y-axis is plotted for both charging and discharging as shown in the rough graph. 2. The time (t = T1/2) corresponding to the intersection of charging curve & discharging curve is noted. 3. The dielectric constant of the material can be calculated by using the value of T1/2 in the given formula. RESULT: Dielectric constant of the given material is found to be K= no unit

17 EXPERIMENTAL ARRANGEMENT TO DETERMINE λ OF LASER SCREEN GRATING n=2 Page 17 n=1 X1 n=0 LASER SOURCE X2 second order first order n=1 n=2 D >1m OBSERVATION Distance between grating and screen is D =... cm To calculate grating constant (d): Width of 500 lines on grating = 1 inch Width of 1 line on grating is = = Hence the distance between 2 consecutive rulings on grating is d = 5.08 X 10-5m

18 DIFFRACTION OF A LASER EXPERIMENT NO: DATE: AIM To determine the wavelength of a given laser using diffraction grating Page 18 APPARATUS: Laser Source, diffraction grating, screen etc. THEORY: The diffraction of light takes place when the size is obstacle (slit) is comparable to the wavelength of light used, the bending of the light at the edges of the obstacle and forms geometrical shadow of the obstacle on the screen is known as the diffraction of light. The grating is the glass plate over which the number of equidistant parallel slits are drawn using diamond point, the line drawn acts as the opaque and the space between the two drawn lines acts as transparent to the light. PROCEDURE 1. The distance between the Grating & the screen has to be adjusted more than 1 metre. 2. Laser is placed on a table and switched ON; the graph is so adjusted such that the diffraction pattern of the laser beam is exactly falls on center of graph sheet placed on the screen. 3. The grating element (500 LPI) is now mounted on the grating stand close to the laser source. 4. Then the diffracted laser spots can be seen on both the sides of central maximum. 5. The centers of various spots of diffraction pattern are marked on the graph sheet using a pencil. Then the graph sheet is removed from the screen. 6. Distance between (X1) first orders, (X2) second orders, (X3) third orders about central maximum.. so on, are measured and tabulated. 7. Diffraction angles for various orders of diffraction can be calculated using formula. θn = tan -1 in degree. where D distances between the grating plate & screen in metre. 8. Hence wavelength of laser for various orders of diffraction can be calculated using the formula. λ= d sinθn n where - d is distance between two consecutive rulings on grating in metre. n is the order of diffraction maxima 9. Average wavelength is obtained. RESULT The wavelength of given laser by diffraction method using grating is λ=.metre.

19 TABULATION TO DETERMINE WAVELENGTH OF LASER Sl.No. Order of diffraction pattern n Distance between various θn = tan-1 Xn orders of diffraction about D central maximum Xn in deg in cm Wavelength of laser λ= d sinθn n CALCULATION PART To calculate wavelength of LASER for nth order. λn = d sin θn in metre n FOR 1ST ORDER λ1 = d sin θ1 in metre 1 Where d grating constant = m θ1 diffraction angle for 1st order =...in degree λ1= = = meter Page 19 in nm

20 CIRCUIT DIAGRAM FOR PARALLEL RESONANCE USING LCR CIRCUIT Band width L ma C AF Oscillator I in ma Page 20 Io 2 Io R 0 f1 fr f2 Frequency in Hz OBSERVATION Inductance chosen L =..in mh Resistance used in the circuit R =..in Ω Capacitance used in the circuit C =..in µf Band width Δf = f2 f1 = in Hz Resonant frequency fr =...in Hz TABULATION FOR PARALLEL LCR RESONANCE CIRCUIT Trial.No. Frequency Current in khz in ma

21 VERIFICATION OF PARALLEL RESONANCE USING LCR CIRCUIT EXPERIMENT NO: DATE: AIM: To study the frequency response of parallel resonance circuit, and determine the value of the unknown inductance, also determine the bandwidth and quality factor of the circuit in parallel Page 21 resonance. APPARATUS: Audio frequency oscillator, standard inductance coil, standard resistors and capacitors, connecting wires etc. [all the components are in-built on the experimental board] PRINCIPLE: This experiment is based on the principle of resonance in AC electrical circuits. An LCR circuit is essentially an oscillator, therefore it will have a definite natural frequency depending on the value of L & C, when the natural frequency of the LCR matches with external applied frequency supplied by the signal or function generator, resonance takes place in the case of parallel LCR circuit at which the current will be minimum, the parallel circuit will be used as a filter circuit. The frequency at which the inductive reactance becomes equal to the capacitive reactance then the circuit is said to be resonance. FORMULA: The unknown Inductance L is given by the formula in henry. Where fr = Resonant frequency in Hz C = Capacitance used in the LCR circuit in μf The Band width of the given Δf = f2-f1 in Hz Series LCR circuit is given by Where f1 and f2 are frequencies as defined in the frequency response curve specimen graph Quality factor Q is given by no unit PROCEDURE: PARALLEL RESONANCE 1. Connect the components, inductance L =200mH and resistance R = 1kΩ in series and capacitance C = 0.01μF in parallel to the L&R, and the function generator as shown in the circuit diagram. 2. Initially the circuit should be closed by switching on the power supply. 3. Set the frequency to 1 khz in the signal generator. 4. The current in the milli ammeter is adjusted for 3mA using the amplitude in the function generator. 5. The signal generator should be adjusted for sinusoidal mode. 6. The frequency is varied insteps of 0.5 khz and note down the corresponding current in each case. 7. At a particular frequency we observe that, the current across the circuit becomes minimum and this frequency is called resonant frequency (fr).

22 TO CALCULATE THE INDUCTANCE OF THE GIVEN INDUCTOR Where = 3.14 f r = resonant frequency C = capacitance used =. = Page 22

23 8. A graph in semi-log graph paper is plotted between current and the frequency and the curve obtained is called the frequency response curve of the given parallel LCR circuit. 9. The bandwidth of the LCR circuit gives us the measure of appropriate frequencies, which the given circuit can pick up when used as a tuning circuit. 10. The band width can be calculated as follows: in the frequency response curve at a value of current equal to Imin x 2 a straight line parallel to frequency axis is drawn which cuts the Page 23 curve at points f1 & f2 called half power frequencies. 11. The frequency difference between f2 & fl is called bandwidth. 12. The quality factor Q indicates degree of sharpness of the resonance curve, which is given by the ratio of resonant frequency (fr) to band width (Δf). RESULT: The frequency response curve is studied, the values of Parallel Resonant frequency fr =.Hz Unknown Inductance L = H Bandwidth Δf =.Hz Quality factor Q =...no unit

24 CIRCUIT DIAGRAM FOR SERIES RESONANCE USING LCR CIRCUIT Imax L ma C AF Oscillator Page 24 I in ma Imax/ 2 Band width R 0 f1 fr f2 Frequency in Hz OBSERVATION Inductance chosen Resistance used in the circuit Capacitance used in the circuit Band width Resonant frequency L =..in mh R =..in Ω C =..in µf Δf = f2 f1 = in Hz fr =...in Hz TABULATION FOR SERIES LCR RESONANCE CIRCUIT Trial.No. Frequency f in khz Current I in ma

25 VERIFICATION OF SERIES RESONANCES USING LCR CIRCUIT EXPERIMENT NO: DATE: AIM: To study the frequency response of series resonance circuit, and determine the value of the unknown inductance, also determine the bandwidth and quality factor of the circuit in series resonance. Page 25 APPARATUS: Audio frequency oscillator, standard inductance coil, standard resistors and capacitors, connecting wires etc. [all the components are in-built on the experimental board] PRINCIPLE: This experiment is based on the principle of resonance in AC electrical circuits. An LCR circuit is essentially an oscillator, therefore it will have a definite natural frequency depending on the value of L & C when the natural frequency of the LCR matches with external applied frequency supplied by the function or signal generator, resonance takes place In the case of series LCR the current at resonance will be maximum, A series LCR will be used as a tuning circuit FORMULA: The unknown Inductance L is given by the formula in henry. fr = Resonant frequency in Hz. C = Capacitor used in the LCR circuit in μf. The Band width of the given Δf = f2-f1 in Hz Series LCR circuit is given by Where Where f1 and f2 are frequencies as defined in the frequency response curve specimen graph Quality factor Q is given by no unit PROCEDURE: SERIES RESONANCE 1.Connections are made as shown in the circuit diagram using the components, inductance L =200mH, Resistance R = 1kΩ, Capacitance C = 0.01μF and the function generator in series. 2.Initially the circuit should be closed by switching on the power supply. 3. Set the frequency to 1 khz in the signal generator. 4. The current in the milli ammeter is adjusted for 0.4/0.6mA using the amplitude in the function generator. 5.The signal generator should be adjusted for sinusoidal mode. 6.The frequency is varied insteps of 0.5 khz and note down the corresponding current in each case. 7.At a particular frequency we observe that, the current across the circuit becomes maximum and this frequency is called resonant frequency (fr).

26 TO CALCULATE THE INDUCTANCE OF THE GIVEN INDUCTOR Where = 3.14 f r = resonant frequency in series LCR circuit C = capacitance used in LCR circuit. =. = Page 26

27 8.A graph in semi-log graph paper is plotted between current and the frequency and the curve obtained is called the frequency response curve of the given parallel LCR circuit. 9.The bandwidth of the LCR circuit gives us the measure of appropriate frequencies, which the given circuit can pick up when used as a tuning circuit. 10.The band width can be calculated as follows: in the frequency response curve at a value of current equal to Imax / 2 a straight line parallel to frequency axis is drawn which cuts the curve Page 27 at points f1 & f2 called half power frequencies. 11.The frequency difference between f2 & fl is called bandwidth. 12.The quality factor Q indicates degree of sharpness of the resonance curve, which is given by the ratio of resonant frequency (fr) to band width (Δf). RESULT: The frequency response curve is studied, the values of Parallel Resonant frequency fr =.Hz Unknown Inductance L = H Bandwidth Δf =.Hz Quality factor Q =...no unit

28 EXPERIMENTAL ARRANGEMENT OF B-H CURVE FOR TRANSFORMER CORE R 1 N 1 PRI. COIL N 2 SEC. S COIL INTEGRAT OR VER.CRO. Page 28 HOR.CRO VER.CRO R 2 C B H hysteresis loop for transformer core OBSERVATION N 1 - Number of turns in the primary coil = N 2 - Number of turns in the secondary coil = R 1 - Resistance between the terminals D-A = R 2 - resistance = C 2 - capacitance used in the circuit = A Area of cross section of the transformer core = L Length of the transformer core = CALCULATION PART To calculate energy loss in the transformer core: Where S V - Vertical sensitiveness of the B-H curve = S H - Horizontal sensitiveness of the B-H curve = in J/cycles/unit volume

29 B-H CURVE FOR TRANSFORMER CORE EXPERIMENT NO: DATE: AIM: To determine the energy loss in the transformer core, using B-H Curve unit. APPARATUS: B-H Curve unit, transformer core, translucent paper etc, THEORY: Page 29 The lagging behind of intensity of magnetization with respect to magnetizing field is known as hysteresis. The energy dissipated in the form of heat in the ferromagnetic material during the cycles of magnetization and demagnetization when it is subjected to the ac fields is called hysteresis loss. Area of hysteresis is the measure of energy loss. The magnetic materials which is strongly attracted by the poles of a strong magnet called ferromagnetic material which characterized by permanent dipoles, spontaneous magnetization and hysteresis. FORMULA: in J/cycles/unit volume Where N 1 - Number of turns in the primary coil = 200turns N 2 - Number of turns in the secondary coil = 400turns R 1 - Resistance between the terminals D-A = 5ohm R 2 - resistance = 4.7kohm C 2 - capacitance used in the circuit = 4.7µF A Area of cross section of the transformer core = 2. 6x10-4 m 2 L Length of the transformer core = 25.4x10-2 m S V - Vertical sensitiveness of the B-H curve in metre. S H - Horizontal sensitiveness of the B-H curve in metre. PROCEDURE: 1. Connect D to A in B-H curve unit, and Connect the Primary & Secondary terminals of the transformer core to respective terminals of a B-H curve unit. 2. Adjust the bright on the centre of CRO using the position knobs 3. Connect Horizontal terminal of B-H curve unit to X input of CRO and vertical terminal of B-H curve unit to the vertical input of the CRO. 4. Switch on the power supply of B-H curve unit, the hysteresis loop is formed. 5. Adjust the Horizontal(X) gain and vertical(y) gain such that the loop occupies maximum area on the CRO screen. Once this adjustment is made, do not disturb the gain controls. 6. Trace the loop on a translucent paper and calculate the area bounded by the loop. 7. Determine the vertical sensitivity (S V ) and horizontal sensitivity (S H ) of the CRO. 8. Energy loss can be calculated using the above formula. RESULT:

30 Energy loss in the transformer core is = in J/cycles/unit volume EXPERIMENTAL ARRANGEMENT OF B-H CURVE FOR FERRITE CORE Page 30 INTEGRAT -OR VER.CRO R 1 PRI. COIL S SEC.COIL HOR.CRO VER.CRO R 2 C B 0 H Hysteresis loop for ferrite core OBSERVATION N 1 - Number of turns in the primary coil = N 2 - Number of turns in the secondary coil = R 1 - Resistance between the terminals D-A = R 2 - resistance used in the experiment = C 2 - capacitance used in the circuit = A Area of cross section of the ferrite core = L Length of the ferrite core = CALCULATION PART To calculate energy loss in the ferrite core: Where S V - Vertical sensitiveness of the B-H curve = in J/cycles/unit volume

31 B-H CURVE FOR FERRITE CORE SEXPERIMENT H - Horizontal sensitiveness NO: of the B-H curve = DATE: AIM: To determine the energy loss in the ferrite material, using B-H Curve unit. APPARATUS: B-H Curve unit, ferrite core, translucent paper etc, THEORY: Ferrites are the electrically insulators, but shows ferromagnetic behavior in the magnetic properties it has the molecular formula MOFe 2 O 3, M stands for Zn ++, Cu ++, Co ++, Ni ++ etc., ferrites are used in the high frequency application where the ferromagnetic materials cannot be employed. FORMULA: in J/cycles/unit volume Where N 1 - Number of turns in the primary coil = 100turns N 2 - Number of turns in the secondary coil = 200turns R 1 - Resistance between the terminals D-A = 5ohm R 2 - resistance used in the experiment = 4.7kohm C 2 - capacitance used in the circuit = 4.7µF A Area of cross section of the ferrite core = 0.913x10-4 m 2 L Length of the ferrite core = x10-2 m S V - Vertical sensitiveness of the B-H curve in metre. S H - Horizontal sensitiveness of the B-H curve in metre. Page 31 PROCEDURE: 1. Connect D to A in B-H curve unit, and Connect the Primary & Secondary terminals of the ferrite core to respective terminals of a B-H curve unit. 2. Adjust the bright on the centre of CRO using the position knobs. 3. Connect Horizontal terminal of B-H curve unit to X input of CRO and vertical terminal of B-H curve unit to the vertical input of the CRO. 4. Switch on the power supply of B-H curve unit, the hysteresis loop is formed. 5. Adjust the Horizontal(X) gain and vertical(y) gain such that the loop occupies maximum area on the CRO screen. Once this adjustment is made, do not disturb the gain controls. 6. Trace the loop on a translucent paper and calculate the area bounded by the loop. 7. Determine the vertical sensitivity (S V ) and horizontal sensitivity (S H ) of the CRO. 8. Energy loss can be calculated using the above formula. RESULT: Energy loss in the ferrite core is = in J/cycles/unit volume

32 EXPERIMENTAL ARRANGEMENT OF THE TO OBTAIN SPECTRUM COLLIMAOTR ADJUSTMENT OF MINIMUM DEVIATION POSITION POSITION GREEN LINE OF SLIT IMAGE MOVEMENT Page 32 TE LE D SC O PE R 1 R 0 ROTATION OF PRISM TABLE OBSERVATION OF SPECTROMETER To calculate least count of the Spectrometer = To calculate the grating constant Where n=1 is the first order spectrum = wavelength of the green spectral line = angle of deviation of green spectral line

33 DIFFRACTION GRATING EXPERIMENT NO: DATE: AIM: To determine the wavelength of the spectral lines of mercury spectrum using a diffraction grating by minimum deviation method. APPARATUS: Page 33 Diffiaction grating, Spectrometer, Spirit level, Mercury vapor lamp. PRINCIPLE: A transmission diffraction grating consists of a large number of parallel equidistant rulings which are drawn using diamond point on a glass plate. These rulings are called opacities and the number of such rulings per unit distance is very significant, because number of rulings per unit distance on the grating plate should be equal to the order of Wavelength of light which passes through the grating plate. This is a necessary condition for diffraction. Each line width will be in the order of wavelength of the incident light hence the incident light undergoes deviation from original path & the phenomenon is named as diffraction. If a white light is incident on such a grating it splits up in to constituent wavelengths, because each component of white light bends through different angle depending on the wavelength of the component. Hence we get a spectrum consisting of a series of spectral lines. Usually we get several sets of spectrum, which are named as orders of spectrum. If λi is the wavelength of a spectral line & DI is the corresponding angle of minimum deviation, then from the theory of diffraction, we have 2CSin DI nλ I 2 Where C is the spacing between two consecutive lines of grating known as grating constant & n is the order of the spectrum. By knowing values of n, C & knowing DI, λi can be calculated. FORMULA: 1) To determine grating constant n g C...m ts Dg 2 Sin 2 Where n = 1 for the first order spectrum Dg = Angle of minimum deviation for green line λg= 5461 X l0-10m, the wavelength of green light Where (1) 2) To determine wavelengths of different spectral lines D m (2) 2 x C x Sin 2 C = grating constant. D = angle of minimum deviation of the respective spectral line.

34 TABULATION TO DETERMINE WAVELENGTH OF THE MERCURY SPECTRAL LINES Direct Reading (R O ) = MSR + (CVD x LC ) = deg Page 34 Spectral Line Yellow-I MSR in deg Spectrometer reading (R) CVD TR= (MSR+CVD X LC) In deg deviation D = R~ R O In deg In A 0 Yellow-II Green Violet CALCULATION PART To calculate wavelength of the spectral lines Where C = grating constant = D = angle of minimum deviation =

35 PROCEDURE: Preliminary adjustments of the spectrometer. 1) Adjusting the Telescope [Mandatory]: The Telescope is turned towards a white wall & the eyepiece position is adjusted such that the cross wires are clearly seen. Then the telescope is focused for a distant object, which is about l0m away from the spectrometer by means of rack & pinion screw of the telescope so that telescope will be able to receive parallel rays. This adjustment should not be disturbed throughout the experiment. Page 35 2) Adjusting the collimator [Mandatory): Light from a mercury lamp is made to fall on the slit attached to the collimator. Collimator, mercury lamp & telescope are brought along a line. By looking through tie telescope the slit is opened and is made narrow, and the image of the slit is made sharp and clear using the rack & pinion screw of the collimator. To obtain the I order spectrum: After making all preliminary adjustments of the spectrometer, find the least count of the spectrometer by noting value of one main scale division & Value of one vernier scale division. Place the diffraction grating on the grating stand, which is mounted on prism table, such that the rulings of the grating plate are parallel to the slit (i.e the width of the plate should be such that it is perpendicular to the incident my). Turn the telescope towards either left or right of the observer until the spectrum is seen, this corresponds to 1st order spectrum. To obtain position of Minimum deviation (See Fig. b): Adjusting the spectrum to the position of minimum deviation is an important step in this experiment, it is mandatory before readings are taken Minimum deviation position is adjusted as follows. 1) Keep the green line in view, now vernier table should be rotated such that the green line moves towards the incident ray which is coinciding with the axis of the collimator (position of the incident ray should be known, it could be towards left of the green line or right of the green line depending on the position of the telescope. 2) As the vernier table is rotated the green line comes closer & closer to the incident ray (slit image), at a particular point we observe that when the vernier table is rotated the green line starts moving away from the incident ray (it takes a back turn). 3) At that point where the green line starts taking back turn vernier table should be fixed which is the position of minimum deviation. The position of minimum deviation for green line is enough and it is not necessary to adjust for all other lines. One should note that at minimum deviation position green line need not coincide with the vertical cross wire. To determine the angle of minimum deviation: After adjusting minimum deviation position readings for all spectral lines starting from Yellow 2 to Violet and slit image (same order should be followed) should be taken by moving the telescope such that vertical cross wire coincides with the respective spectral line. The readings are tabulated in the given tabular column. The difference in the reading of the given spectral line and the reading of the slit image (Direct reading) gives angle of minimum deviation (D) for the given spectral line. Calculation of grating constant: Grating constant C can be calculated using the Formula (1)

36 RESULT: The Wavelengths of (1) Yellow 2 = A (2) Yellow1 = A (3) Green = A (4) Violet = A Page 36

37 VIVA QUESTIONS DIFFRACTION GRATING 1. What is a plane grating? 2. What is meant by grating constant? 3. Explain the physical significance of grating constant. 4. Explain the phenomenon of diffraction. 5. How many classes of diffraction are there, and what is the difference between them. 6. How do you distinguish between diffraction and refraction? 7. What are the different parts of spectrometer and mention their functions? 8. Why do we focus the telescope of spectrometer to a distant object before we start the experiment? 9. What is the function of a collimator? 10. What is the condition to cause diffraction of light? 11. What is meant by angle of minimum deviation? Why do we set it? 12. What will be the resulting spectrum if we use a monochromatic light such as sodium vapour light? 13. Why a spectrum cannot appear in the direct reading position? 14. Why the spectrum due to diffraction appears in reverse order when compared to that obtained by dispersion using prism? 15. Why do we consider only first order spectrum for the experiment? TRANSISTOR CHARACTERISTICS 1. What is a transistor? 2. Explain the conduction process across a P-N junction in the forward bias. 3. What are input characteristics curves? What information we can get from input characteristics curves? 4. Explain the terms depletion region, barrier potential. 5. Explain how a transistor can function as a switch. 6. What are the different configurations in which a transistor can be used in a circuit? 7. Why the output resistance is much greater than the input resistance in the CE mode? 8. Define current gain. 9. What is the difference between a PNP transistor and an NPN transistor? 10. What do you mean by doping? 11. What is the reason for keeping emitter-base junction under forward bias and base-collector junction under reverse bias? 12.Explain the mechanism of amplification in an npn transistor under CE mode. B-H CURVE 1. What is ferromagnetic substance? 2. What is intensity of magnetization? 3. Define the terms Permeability, Retentivity and Coercievity. 4. What is hysteresis? 5. What do you mean by cycle of magnetization? 6. What is the application of hysteresis? 7. Define Magnetic susceptibility and Permeability. 8. How a ferromagnetic substance undergoes magnetization Page 37

38 SERIES AND PARALLEL RESONANCE. 1. What are inductor, capacitor and resistor? 2. What are active and passive circuit elements? 3. What is resonance? 4. Why current is maximum at resonance in series resonance circuit? 5. Why current is minimum at resonance in parallel resonance circuit? 6. What is meant by quality factor? 7. If the frequency of applied signal is increasing, what will be the response of resistor, inductor and capacitor? 8. Is it possible to arrive at resonance without a resistor in either series or parallel LCR circuit? 9. What do you mean by sharpness of resonance? 10. Why series resonance circuit is called an acceptor circuit? 11. Why parallel resonance circuit is called a rejector circuit? Page 38 DIELECTRIC CONSTANT. 1. What are dielectrics? 2. What is the significance of dielectric constant? 3. What is the role of dielectric material in a capacitor? 4. What are the applications of dielectric materials? 5. What are the different types of dielectrics? 6. What is Static and Dynamic dielectric constant? 7. What is Polarization? 8. What are types of polarization? 9. What are polar, non polar, Ferro & piezo electrics? 10. What is Curie temperature? STEFAN S LAW 1. What is a black body? 2. What is the application of Stefan s law? 3. State other laws related to black body radiation. 4. What are the values of Absorption, Reflection and Transmission coefficients for a black body? 5. What is Ferry s black body? 6. Under what condition does a black body emit radiation? 7. Which law of black body is most acceptable? 8. List two important features of blackbody spectrum. 9. What are Steady state, conduction, convection,radiation,temperature & properties of thermal radiation.

39 V-I CHARACTERISTICS OF ZENER DIODE 1. What is a P-N junction diode? 2. Explain how conduction takes place in the forward and reverse bias. 3. What is the difference between a junction diode and a zener diode? 4. Explain the terms knee voltage and breakdown voltage. 5. Which are the important types of breakdown mechanisms, and explain them. 6. Give an application of zener diode. 7. What is dynamic resistance and explain the variation in the resistance of the device for different voltages. PLANCK S CONSTANT 1. What is Planck s constant? 2. What are Planck s black body radiations? 3. What is emissivity & absorptive power? 4. State Kirchhoff s black body radiation law. 5. Why LED s emits different colors? 6. What is LED? 7. What is the unit of energy gap? 8. What is the difference between semiconductor diode & LED? 9. What is the energy gap for insulators, semiconductors & conductors? 10. What is black body? 11. State Wien s displacement law? Page 39