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Department of Applied Sciences LAB MANUAL Basic Electrical & Electronics Lab (BTEE 102) B.Tech 1st Year – All branches [2012-13]t of V KCT COLLEGE OF ENGG & TECH, FATEHGARH Punjab Technical University LAB MANUAL KCT College of Engg. & Tech. Department- AS INDEX Sr no Name of Experiment 1 To experimentally verify the ohm’s law 2 To verify Kirchhoff's Voltage law in a series circuit and parallel circuit 3 To find voltage, current relationship and power factor of a given R-L circuit 4 To find out the line voltage, phase voltage relationship, line current and phase Current relationship in case of star-connected and delta connected, 3-phase balanced load. 5 6 To measure resonance in AC circuits To study Hysteresis property of the given magnetic material 7 Full-Wave Rectification 8 To verify the working of LVDT 9 Semiconductor (or crystal) diode characteristics. 10 To study the truth table of all the gates 11 12 To study the input and output characteristics of a PNP/ NPN transistors in common base configuration To perform open-circuit and short-circuit test on a transformer 13 To study the speed control of a dc shunt motor 14 To connect, start and reverse the direction of rotation of a 3-phase induction motor. BEEE Lab 1 KCT College of Engg. & Tech. Department- AS EXPERIMENT-1 Objective: To find voltage, current relationship and power factor of a given R-L circuit. Apparatus Required: Variac or 1-phase auto-transformer-1, Single-phase ac load [or lamps and choke coils], Moving-iron voltmeter [0-250 V]-1, Moving iron ammeter [0-5 A]-1, Dynamometer .~-pe wattmeter (250 V, 5 A)-1, Double pole, single throw switch (DPST Switch)-1, Connecting ieads. Theory: Current flowing through an ac circuit is given as I= V/Z where V is the ac supply voltage (voltage applied to the circuit) and Z is the impedance of the circuit in ohms. Power factor of an ac circuit is given as P Power factor, cos ~ = VI Where P is power of the given load circuit in watts, V is the voltage applied to the circuit in volts and I is the current in amperes flowing through the circuit. Connection Diagram: Procedure: Variac, ammeter, wattmeter, voltmeter, load, (lamps in series with choke coils) are connected, through double pole single throw switch, to single phase BEEE Lab 2 KCT College of Engg. & Tech. Department- AS supply mains as shown in fig. 1. The readings of ammeter, voltmeter and wattmeter are noted for var~ous settings of variac. Observations: S.No. Voltmeter Reading, Ammeter Reading, V in Volts 1. 2. 3. 4. Wattmeter Power Factor of I Reading, the Circuit, in Amperes P in Watts Cos ~ = P VI Conclusion: 1. Current I increases directly in proportion to applied voltage V. 2. Power factor of the circuit is same through out for a given load. Note: If required, the readings of the instruments can be recorded with the different loads (by varying the number of lamps and chokes connected in series). BEEE Lab 3 KCT College of Engg. & Tech. Department- AS EXPERIMENT-2 Objective: To find out the line voltage, phase voltage relationship, line current and phase Current relationship in case of star-connected and delta connected, 3-phase balanced load. Apparatus Required: TPIC switch (500 V, 15 A)-1, Moving iron type voltmeter (0500 V)-2, Moving iron ammeter (0-10 A)-2, 3-phase balanced load (say a 3-phase, 440 V, 50 Hz, 7.5 kW induction motor), Board containing six open terminals-1 and Connecting leads. Theory: In star-connections Line voltage, VL =~ p h as e vo lt age =~ V p Line current, IL = Phase current, Ip In deltaconnections Line voltage, VL = Phase voltage, Vp Line current, IL =~ phase current I p Connection Diagram: BEEE Lab 4 KCT College of Engg. & Tech. Department- AS Procedure: The connections of the terminal box of the induction motor to the stator phase windings of the motor are shown in fig. 3.3 (a). First of all the connections in terminal box are made, as shown in fig. 3.3 (b). The motor is started and put on load and readings of both voltmeters and ammeters are noted for different loads on the motor. Now the TPIC switch is made off and the connections in terminal board are changed, as illustrated in fig. 3.3 (c) for delta connections. The motor is started and put on load and the readings of both ammeters and voltmeters are noted for different loads on the motor. Connection S. No. ~ Voltmeter s Star Delta Reading Vl, 1 2 3 l Voltmeter Ammeter Reading V2, Reading Al, Line Voltage Phase Voltage Line Current in Volt5, VI Ammeter V~ ~ Vp IP in Volts, Vp in Amperes, IL Reading A2, Phase Current in Amperes, Ip 23 Results : In star connections, line voltage V comes out to be ~ times phase voltage Vp and line current IL comes out to be equal ~o phase current Ip. In delta connections, lines voltage V L comes out ,;o be equal to phase voltage V p and line current IL comes out to be times ~ phase current Ip BEEE Lab 5 KCT College of Engg. & Tech. BEEE Lab Department- AS 6 KCT College of Engg. & Tech. Department- AS Experiment-3 Objective: To perform open-circuit and short-circuit test on a transformer and determine the following: (a.) the transformation ratio. (b) the transformer efficiency at 25%, 50%. 75%, 100%, l50% load at pf of 0.8 lagging and to pplot the characteristic Apparatus Required: Single phase transformer (preferably 1 kVA with one winding rated at 230 V)-1, V ariac-1, Low range voltmeter-1, Low range ammeter-1, Low range low power factor wattrneter-1, W~attmeter, ammeter and voltmeter of normal ranges (depending upon the rating of transformer under test) one each, DPIC switch-1 and connecting leads. Theory: Open-circuit test is performed to determine the iron loss and the transformation ratio. Since during this test no current flows in the open-circuited secondary, the current in the primary is merely that necessary to magnetise the core at normal voltage. Moreover, the magnetising current is very sma11 fractioii of the fullload current (usually 3 to 10 per cent of full-load current) and may be neglected as far as copper loss is concerned consequently, this test gives this core loss alone practically. The transformation ratio, K-_ Secondary turns _ Secondary voltage on opencircuit Primary turns Voltage applied to primary =V2 / V1 The short-circuit test is performed to determine the full-load copper loss. In this test ~ince the terminals of the low voltage winding are short-circuited, therefore, the trans:ormer becomes equivaTent to a coil having animpe~arice -equal--t-o the impedance of both the windings. The applied voltage is very small as it is adjusted to cause flow of rated current in the windings, so the flux linking with the core is very small and, therefore, iron losses are negligible. The power drawn from the supply, therefore, represents full-load copper loss. Transformer efficiency at any given load is given as _ Output ______________ x 100 Output + iron loss + copper loss at given load where Output = Voltmeter reading in open-circuit test, Vl BEEE Lab 7 KCT College of Engg. & Tech. Department- AS x ammeter reading during short-circuit test, I5 x pf Iron loss, Pi = Power input in open-circuit test with rated voltage = P o and Copper loss, P~ = Power input in short-circuit test Connection Diagrams: See figures 8.20 and 8.21 Procedure: 1. (ipen-circuit Test. The transformer is connected, as shown in fig. 8.20 on the low voltage side. The ammeter A is a low range ammeter and W is a low range and low power factor wattmeter. The high voltage side is kept opencircuited. AC supply at rated voltage is switched on to the transformer through DPIC switch. High range voltmeter V2 is connected across the secondary of the transformer. Readings of voltmeters V l and V2, ammeter A and wattmeter W are noted and tabulated as below. 2. Short-circuit test. The transformer is connected as shown in fig. 8.21, the low voltage winding is short-circuited by connection having negligible resistance and good contacts. The voltage applied to the primary is increased in steps so that ammeter A carries 0.25, 0.5, 0.75 time rated current, rated current, and 1.5 times rated current. The efficiency of the transformer is calculated at different loads as mentioned above and a curve is plotted between efficiency and load current. Observations: (i) Open-circuit test: Primary voltmeter reading, V l = ........ Secondary voltmeter reading, V 2 = ....... Input power on no load, P o = Wattmeter reading, W= ......... V_ Transformation ratio, K = V l ................... (ii) Short-circuit test: Rated primary current, Rated kVA X 1,000 I - _ ........... f Rated primary voltage Power factor, cos ~ = 0.8 (lag) BEEE Lab 8 KCT College of Engg. & Tech. S. No. Department- AS Ammeter Reading Wattmeter Reading in Amperes, IS in Watts, PS Transformer Efficiency, V~ Is cos~ ~~ = _ x Vlls cos~+P o+Ps 100 Vlls x0.8+P V~Is ax +P 0.8s x 1. 2. 3. 4. 5. 100 Result: 1.During short-circuit test, power input, P S varies as the square of the input current, I5 i.e. copper loss varies as the square of the load current. 2. The curve plotted between the transformer efficiency and load current [fig. 4) shows that the efficiency becomes maximum when copper loss equals iron loss. BEEE Lab 9 KCT College of Engg. & Tech. Department- AS EXPERIMENT-4 Objective: To study the speed control of a dc shunt motor and to draw the speed variation with respect to change of (a) field current (field control) and (b) armature current (armature control). Apparatus Required: 250 V dc shunt motor of capacity, say, 2 kW-1, PMMC ammeter (0-2.5 A)-1 and (0-10 A)-1, Rheostats-high resistance, low current-1 andlow resistance, high current-1, Tachometer-1, DPIC switch-1 and Connecting leads. Theory: The speed of a dc shunt motor is given as Hence the speed of a dc shunt motor can be changed by either changing the shunt fie7d azn~xit h~~ (by inserting an external resistance in the field circuit) or changing the back emf, Eh, (i.e. V- IQ Ro) by inserting an external resistance in the armature circuit. Connection Diagram: Procedure: The connections are made, as shown in fig. 10, and the rheostats are put in zero positions. The dc supply is switched on by closing the DPIC switch. Field control: The reading of ammeter A1 is noted and the speed of the motor is measured by tacliometer. Now the field rheostat setting is changed in steps (increasing the resistance) BEEE Lab 10 KCT College of Engg. & Tech. Department- AS and ammeter Al readings are noted and the motor speed is measured and recorded. Now the field rheostat setting is brought back to zero. Armature Control: Resistance is increased in steps in the armature circuit for armature resistance control. The ammeter A z readings are noted and the motor speeds are measured and recorded. Armature control rheostat is brought back to zero and the supply is switched off through DPIC switch. Observations: S.No. Field Control Armature Control Ammeter A1 Read- Speed of Motor Ammeter A~ Read- Speed of Motor ings in Amperes, Ish in RPM ings in Amperes, Io in RPM 1 2 3 4 5 Result: l. With the increase in resistance in the field circuit, the field current decreases i.e. field becomes weaker and, therefore, speed increases. 2. With the increase in resistance of the armature circuit, voltage drop in armature increases i.e. back emf Eh decreases and, therefore, speed decreases. BEEE Lab 11 KCT College of Engg. & Tech. Department- AS EXPERIMENT-5 Objective: To connect, start and reverse the direction of rotation of a 3-phase induction motor. Apparatus Required: Three phase induction motor-1, Star-delta starter-1, TPIC switch1, Tools such as screw driver, plier, test pen etc. and connecting leads. Theory: Motor is connected to the 3-phase ac supply mains through star-delta starter and TPIC switch, as shown in fig. 11 (a). The direction of rotation of a 3-phase induction motor can be reversed by interchanging any two terminals at the TPIC switch, as shown in fig.l l(b) Procedure: The connections of a 3-phase induction motor are made to the stardelta starter and to the TPIC switch, as shown in fig. 11 (a). The TPIC switch is closed and the motor is started !-y taking the lever of the starter to the start (star) position and then with a jerk to the run position (or delta connections). The direction of the rotation of the motor is observed. Say, it is in clock-wise direction. Now the motor is stopped by pushing the stop button and supply to the motor is r'emoved by opening the TPIC switch. The two leads of the motor are interchanged to the T1~I~C\switch, as shown in fig. 11 (b). TPIC switch is closed and the motor is started again. Tl,~e direction of rotation of the motor is observed. The push button is pushed and the TPIC switch is made off. Observations and Results: The direction of rotation of the motor in second case BEEE Lab 12 KCT College of Engg. & Tech. Department- AS is found opposite to that in first case. EXPERIMENT NO 6 BEEE Lab 13 KCT College of Engg. & Tech. BEEE Lab Department- AS 14 KCT College of Engg. & Tech. Department- AS Procedure : lnsert IC 7432 on the IC base of the logic experimental trainer board. Give + 5 V input to pin 14 and graund pin 7. Give inputs A and B to pins 1 and 2 using binary switches. Connect output pin 3 to LED. ~witch on the trainer. Observe LED output. Try with different combinations of t A, B. Prepare truth tabie. Repeat for other gates. BEEE Lab 15 KCT College of Engg. & Tech. BEEE Lab Department- AS 16 KCT College of Engg. & Tech. Department- AS EXPERIMENT NO 7 Title: Semiconductor (or crystal) diode characteristics. Objective: 1. Trace the circuit meant to draw the diode-characteristics; 2. Measure the current through the diode for a particular value of forward voltage; 3. Plot the forward characteristics of a germanium and a silicon diode; 4. Compare the forward characteristic of a Ge diode with that of a Si diode; 5. Calculate the forward static and dynamic resisrance of the diode at a particular operating point. APPARATUS REQUIRED: Experimentai board, regulated power supply, milliammeter, electronic multimeter. CIRCUIT DIAGRAM: The circuit diagram is given in Fig. Brief Theory: A diode cr5~duets in forward bias (i.e. when its anode is at higher poi~ntiai than its cathode). It does not conduct in reverse bias. When the diode is forward-biased, the barrier potential at junction reduce~. The majority carriers then diffuse across the junction. This causes current to flow through the diode. In-reverse bias, the barrier -potential increases, and almost no current can flow through the diode. The external battery is connected so that its positive terminal goes to the anode and its negative terminal goes to cathode. The diode is then forward biased, The amount of forward bias can be varied by changing the externally applied voltage. As shown in BEEE Lab 17 KCT College of Engg. & Tech. Department- AS Fig. E.4.1.1, the external vo7tage applied across the diode can be varied by the potentiometer Ri. A series resistor (say, 1 ks2) is connected in the circuit so `that excessive current does not flow through the diode. VVe can note down different values of the current through the diode for various values of the v~lta,ge across it. A nlat between this voltage and current gives the clzode forward characteristics At a given operating point we can determine the static rcsastance (Ra) and dynamic resistance (ra) of the diode T'rom its characteristic. The static resistance is defined as the ratio of the dc voltage to dc current, i.e. Rd =V/I The dynamic resistance is the ratio of a small change in voltage to a- small ~hange in current, i.e. PROCEDURE: 1 Find the type number of the diodes connected in the experirnental board. 2. Trace the circuit and identify different components used in the cii•cuit. Read the value of the resistor using the colour code. 3. Connect the milliammeter and voltmeter of suitable ranges, say, (i, to 25 mA for ammeter and 0 to 1.5 V for voltmeter. 4. Switch on the pawer supply. With the help of the potentiometer R t, increase the voltage slowly. 5. Note the milliammeter and voltmeter readings for each setting of t~e potentiometer. Tabulate the observations. 6. Draw the graph between voltage and current. 7 At a suitable operating point, caiculate the static and dynamic resistance of tlte diode, as illustrated in Fig. E.4.L2. BEEE Lab 18 KCT College of Engg. & Tech. BEEE Lab Department- AS 19 KCT College of Engg. & Tech. BEEE Lab Department- AS 20 KCT College of Engg. & Tech. Department- AS Experiment no 8 Objectives: To experimentally verify the ohm’s law. Apparatus: DC Power Supply DC current source Few Resistors Wheatstone bridge Multimeter THEORY: Ohm’s Law: The voltage across an element is directly proportional to the current through it. The ohm’s law can be written mathematically as: V IR where R = Resistance V = voltage across the resistance R I = Current through the resistance R PROCEDURE: A. Ohm’s Law: 1. 2. 3. 4. Connect the circuit as shown in figure 2. Set the DC voltage supply to 10 Volts. Set the resistance R to 100 ohms. Measure the voltage across the resistor and the current through the resistor and write the results in Table 1. 5. Determine the value of the resistance using Ohm’s law R=V/I and record in the Table 1. 6. Repeat step 2 to 5 for the other resistors (1000 ohms, 10 K ohms). BEEE Lab 21 KCT College of Engg. & Tech. Department- AS 1 K ohms R Vs=10V Figure 1: Ohm's Law TABLE 1 Resistor (Nominal Value) 100 1 K 10 K Ohm-meter Reading R=V/I Percent Deviation from Nominal Value Percent Deviation = (Nominal Value – Ohm-meter Reading) / (Nominal Value) BEEE Lab 22 KCT College of Engg. & Tech. Department- AS EXPERIMENT NO 9 Kirchhoff’s Laws Objective: To verify Kirchhoff's Voltage law in a series circuit. To verify Kirchhoff's Current law in a parallel circuit. Series Circuit R1 VS = 10V Kirchhoff's Voltage law: = IR1 + IR2 junction R2 Parallel Circuit VS = 10V VS = VR1 + VR2 R1 R2 Kirchhoff's Current law: IT in a loop at a Part A - Series Circuit: 1. Calculate the total resistance, circuit current and voltage drop across each resistor if wired in a series circuit as shown in the figure. Total Resistance: Circuit Current: Voltage Drop across the 470 Ohm Resistor, R1: Voltage Drop across the 1K Ohm Resistor, R2 : Power-supply Voltage using Kirchhoff's Voltage law : (should be equal to the sum of the voltage drops) 2. Obtain a 470 Ohms and a 1K Ohms resistors and make sure you got the correct ones. Measure and record their actual resistances. R1 = ___________________ R2 = ___________________ 3. Using the Breadboard, connect the resistors in SERIES as shown in the figure below: R1 is the 470 Ohm resistor and R2 is the 1K Ohm resistor. R1 BEEE Lab R2 23 KCT College of Engg. & Tech. Department- AS 4. Measure the total circuit resistance. Total Resistance: 5. Connect the Power-supply to the SERIES resistors as shown in the figure below. 6. Set the Power-supply to 10 Volts. 7. Measure the voltage drop across each resistor and the Power-supply voltage. Voltage Drop across the 470 Ohm Resistor: Voltage Drop across the 1K Ohm Resistor: Power-supply Voltage (should be equal to the sum of the voltage drops): 8. Verify that all the measured values tally (matches) with the calculated values. Part B - Parallel Circuit: 1. Using the Breadboard, connect the PARALLEL circuit. R1 is the 470 Ohm resistor and R2 is the 1K Ohm resistor. 2. Calculate the current flow through each of the resistors, and the total circuit current. To calculate current through each of these resistors use ohm’s law: I = V/R Current through: IR1 = IR2 = Total Circuit Current using Kirchhoff's Current law : Total Circuit Current using Ohm’s law : IT = IT = VS / RP = ? 1/RP = 1 / R1 + 1 / R2 RP = ( R1 + R2 ) / ( R1 x R2 ) R1 R2 RP R1 is the 470 Ohm resistor and R2 is the 1K Ohm resistor. BEEE Lab 24 KCT College of Engg. & Tech. Department- AS RP = ? 3. Measure the current flow through each of the resistors, and the total circuit current. Current through: IR1 = Total Circuit Current: IT = IR2 = 9. Verify that all the measured values tally (matches) with the calculated values. BEEE Lab 25 KCT College of Engg. & Tech. Department- AS EXPERIMENT 10 Title: to measure resonance in AC circuits INTRODUCTION In this experiment the impedance Z, inductance L and capacitance C in alternating current circuits will be studied. The parameters of the circuit will be varied to produce the condition called resonance. The inductive and capacitive reactance are defined as follows: Inductive Reactance = XL = 2fL Capacitive Reactance = XC = 1 . 2fC XL The impedance in a series AC circuit is found by adding the individual reactances and resistance as vectors as shown in Figure 1. Z XC XL XC R Fig. 1 Voltages are all equal to the current I, times the individual or combined reactances. They can be calculated from a diagram which has the same form as that shown in Figure 2. VL = IXL VC = IXC Vtotal = IZ VL V C VR = IR Fig. 2 As the frequency is varied from low to high, a minimum value of total impedance Z is 1 found when XL = XC, or f = . The value of Z at this resonance frequency is Z = 2 LC BEEE Lab 26 KCT College of Engg. & Tech. Department- AS R. If the applied voltage is kept constant, then when Z is a minimum, I will be at a maximum, so both Z and I have the general form as shown in Figure 3. Z I f f Fig. 3 I The width of the curves in the above is of great importance in such devices as radio and TV receivers (we only want one channel at a time), and is measured by the ratio of the width to the center frequency, as shown in Figure 4. Imax Small R 0.707 Imax Larger R f1 fo f2 f Fig. 4 When the peak is narrow, the circuit is said to have a high Q, where the quality Q is defined as: Q = fo f2 f1 . A high Q corresponds to a small value of the total series resistance (coil resistance plus any other resistance). Q can also be Z for f = f 2 XL XC = R Z for f = f o (Z = R) Z for f = f 1 45o 45o XC XL = R X shown to be given by Q = L , R where XL = 2foL, with fo being the resonant frequency. Figure 5 indicates the relationship between Z, R, XL and XC as f varies from f1 to fo to f2. BEEE Lab Locus of points as f varies Fig. 5 27 KCT College of Engg. & Tech. Department- AS EQUIPMENT & MATERIALS clips Simpson 420 function generator Decade capacitor box 100- composition resistor Banana wires 2 multimeters Frequency counter Oscilloscope Inductor, 0.01 Henry 2 alligator 2 BNC-to-banana adapters triangle Coaxial cable, BNC ends French curve Plastic 1 sheet of graph paper EXPERIMENTAL PROCEDURE A. Capacitive and Inductive Reactance 1. Set up the circuit as shown in Figure 6. Both multimeters must be dialed to V to act as AC voltmeters. Set the decade capacitance box to 0.5 F. Use alligator clips to connect the 100- resistor in the circuit. Use the coaxial cable to connect the function generator’s TTL output to the frequency counter’s A input, and use the counter to set the frequencies accurately by using the “A Input”, setting the counter for a 1 second gate time, and a frequency setting of <10MHz. Set the function generator to maximum amplitude. V V 100 5.0 X 107 F Fig. 6 2. Take voltage readings across the function generator and resistor for each frequency setting. Frequency settings may be made from 2,000 Hz to 10,000 Hz in 2,000-Hz steps. 3. From Fig. 2, the voltage across the function generator V fg (= Vtotal) is the vector sum of the voltage across the resistor VR and the voltage across the capacitor V C. From the right-angle triangle, Vfg2 = VR2 + VC2. Use this equation and the observed values of voltage to calculate VC. 4. Ohm’s law for the resistor is VR = IR. Calculate the current through the resistor. 5. Ohm’s law for the capacitor is VC = IXC. Because the resistor and capacitor are in series, they experience the same current. Calculate the measured reactance X C. 6. Theoretically, the reactance of a capacitor is X C = 1/2fC. Calculate this value and determine the percent difference between this and the measured value. A reasonable agreement between these two values of X C validates the vector calculation of V C and the theoretical calculation of XC. Notice that the equation Vfg = VR + VC, BEEE Lab 28 KCT College of Engg. & Tech. Department- AS appropriate for a DC circuit, does not match your data for this circuit. 7. Repeat the above procedure with the 10-mH inductor in the circuit instead of the capacitor. For an inductor, Vfg2 = VR2 + VL2 and VL = IXL. Theoretically, the reactance of an inductor is XL = 2fL. B. RLC Series Resonance 1. Set up the apparatus as in Figure 1, by connecting the output of the function generator in series to the Hewlett-Packard multimeter (set to mA to make it an ammeter), the 10 mH inductor, the decade capacitance box set to 0.10 F and the 100- resistor held by alligator clips. Turn on the ammeter and press the AC/DC button (beside the Range button) to produce a ~ sign in the display. This indicates that the ammeter will measure AC instead of DC current. Attach a BNC-to-banana adapter to the Ch 1 input of the oscilloscope, and connect its positive input to the positive output of the function generator. The TTL output of the function generator should remain connected to the A input of the frequency counter. L C A R ~ Oscilloscope Ch. 1 Fig. 7 2. Calculate the theoretical values of the resonance frequency f o, the bandwidth and the quality from the values of resistance, inductance and capacitance. 3. Measure the root-mean-square current I on the multimeter over a range of frequencies, starting with f = 2000 Hz and increasing by 500-Hz intervals. Maintain Vtotal at 0.40 V peak-to-peak by monitoring the amplitude of the sine wave on the oscilloscope and adjusting the amplitude of the function generator. A setting of 0.2 Volts/div gives a convenient size to the sine wave, and should peak 2 squares above and 2 squares below the center-line. The wave can be centered by rotating the POSITION dial on the oscilloscope. Place the measurements in Data Table 3. 4. Plot current I vs. frequency f on a piece of graph paper. Obtain extra readings as necessary near the resonance frequency to clearly define the resonance peak. Use a French curve to connect the data points as smoothly as possible. 5. Find f1 and f2 from this graph as the frequencies for which I = 0.707 Imax , as shown in Figure 4. Calculate fo as the average of f1 and f2, and calculate the bandwidth and quality from the values of f 1 and f2. Find the percent difference of these three quantities from their theoretical values. BEEE Lab 29 KCT College of Engg. & Tech. Department- AS LABORATORY REPORT: AC CIRCUITS AND RESONANCE Part A: Data Table 1: Capacitive Reactance Frequency (Hz) Voltage across function generator (V) Voltage across resistor (V) Voltage across capacitor (V) Current (A) Measured reactance () Calculated reactance () 2000 4000 6000 8000 10,000 4000 6000 8000 10,000 Percent difference Data Table 2: Inductive Reactance Frequency (Hz) Voltage across function generator (V) Voltage across resistor (V) Voltage across inductor (V) Current (A) Measured reactance () Calculated reactance () BEEE Lab 2000 30 KCT College of Engg. & Tech. Department- AS Percent difference Data for Part B: R = ___________ __________ L = C = ___________ fo = 1 2 LC = __________ Bandwidth = __________ R = ___________ 2L Q= 2f o L = R Data Table 3 Source Frequency f (Hz) I (A) Source Frequency f (Hz) I (A) 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 Experimental values from graph: f1 = ________________ Hz f2 = ________________ Hz Resonance frequency = fo = ________________ Hz BEEE Lab % difference = 31 KCT College of Engg. & Tech. Department- AS ______________ Bandwidth = f2 f1 = ________________ Hz ______________ Quality = ______________ BEEE Lab fo = ________________ f 2 f1 % difference = % difference = 32 KCT College of Engg. & Tech. Department- AS Experiment 11 B-H Curve Aim: To study Hysteresis property of the given magnetic material and hence to determine a) Energy loss /cycle/ unit volume b) Remnant Flux Density and c) Coercive Field Strength. Apparatus: Specimen, B-H Curve tracer unit, Cathode Ray Oscilloscope (CRO). Formula: Energy loss is determined using the formula S S A PL ENvH 0.5 J/ per cycle/unit volume, Where N is the Number of turns in the coil (300), P is the resistance in series with the coil (65), L = Length of the coil (0.033m) and SH and SV are the horizontal, vertical sensitivities of the CRO and A= Area of the loop. The Coercive field is determined from the formula A turns m-1 PL H N OC SH C The Remnant flux density = 2 0 0.5 B OB S WbmV Procedure: Initially the following settings are made for CRO. The CRO is switched on and is set to X-Y mode. The bright spot is adjusted to the centre of the display with the help of Horizontal and Vertical shift knobs. Both the channels (X-Channel (Horizontal,CH1) and Y-Channel (Vertical, CH2 ) are set to AC mode. One terminal of the magnetizing coil is connected to point C of the main unit and the other Terminal to any of the point between V1 to V3 (V3 is recommended). Outputs X & Y of the main unit are connected respectively to CH1 & CH2 of the CRO. IC probe and the Supply (P.S) are connected to the main kit. The main kit is switched on. The BEEE Lab 33 KCT College of Engg. & Tech. Department- AS resistance (P) is set for maximum value with the help of the given knob. With no specimen, the horizontal gain of the CRO is adjusted until a convenient X deflection is obtained on the CRO display. Specimen is inserted through the coil such that it touches only the probe at the centre not the conducting tracks. The Y gain of the CRO is adjusted to get appropriate Loop. Trace the loop on the graph paper by reading coordinates of the points A, B, C, D, E, F on the loop in CRO and area of the loop is Measured. a) Energy loss is determined using the formula S S A PL ENvH 0.5 J/ per cycle/unit Volume, b) OC is measured from the graph. The Coercive field is determined from the formulaA turns m1 PL H N OC SH C c) OB is measured from the graph. The Remnant flux density is determined using the Formula 20 B 0.5 OB S WbmV Result: The Energy loss in the specimen= ……………..J/cycle/cubic meter The Remnant Induction=……………..Wb m-2 The Coercive field = ……………...A turns m-2 BEEE Lab 34 KCT College of Engg. & Tech. BEEE Lab Department- AS 35 KCT College of Engg. & Tech. Department- AS Experiment no.12 Transistor characteristics BJT Aim: To study the input and output characteristics of a PNP/ NPN transistors in common base configuration Equipment: Power Supply ( 0-15V), DMMs and potentiometer and other components. Theory Circuit Diagrams: VCC Transistor used CK100 Fig: Common Base Configuration of PNP transistor Procedure: A. Common Base configuration 1. For the input characteristics of common base configuration, set-up the ckt of fig 4.1. Set VEE around 5-6 V and do not change it during the experiment (why?). Now vary VEB with the potentiometer and record IE keeping VCB at zero volt. Observations may be recorded up to a maximum of 30mA emitter current. Repeat the observations (for four sets) for various values of VCB from 0 to 10 V. 2. For output characteristics follow the ckt of fig 4.1. Set V EE around 5-6 V and do not change it during the experiment. Set IE =0 with the pot and record the IC as a function of VCB (from 0-10V). Record at least four sets of O/p curve by varying IE from 0-20mA. 3. Plot all the curves. Plot the load line. Find input and output resistances and current gain dc. BEEE Lab 36 KCT College of Engg. & Tech. Department- AS Experiment Title: to verify the working of LVDT Objectives: Measuring voltage with displacement variation using Linear Variable Differential Transformer (LVDT). Apparatus: LVDT Micrometer for LVDT Voltmeter Theory: The Linear Variable Differential Transformer is a position sensing device that provides an AC output voltage proportional to the displacement of its core passing through its windings. LVDTs provide linear output for small displacements where the core remains within the primary coils. The exact distance is a function of the geometry of the LVDT. An LVDT is much like any other transformer in that it consists of a primary coil, secondary coils, and a magnetic core. An alternating current, known as the carrier signal, is produced in the primary coil. The changing current in the primary coil produces a varying magnetic field around the core. This magnetic field induces an alternating (AC) voltage in the secondary coils that are in proximity to the core. As with any transformer, the voltage of the induced signal in the secondary coil is linearly related to the number of BEEE Lab 37 KCT College of Engg. & Tech. Department- AS coils. The basic transformer relation is: where: Vout is the voltage at the output, Vin is the voltage at the input, Nout is the number of windings of the output coil, and Nin is the number of windings of the input coil. As the core is displaced, the number of coils in the secondary coil exposed to the coil changes linearly. Therefore the amplitude of the induced signal varies linearly with displacement. The LVDT indicates direction of displacement by having the two secondary coils whose outputs are balanced against one another. The secondary coils in an LVDT are connected in the opposite sense (one clockwise, the other counter clockwise). Thus when the same varying magnetic field is applied to both secondary coils, their output voltages have the same amplitude but differ in sign. The outputs from the two secondary coils are summed together, usually by simply connecting the secondary coils together at a common center point. At an equilibrium position (generally zero displacement) a zero output signal is produced. The induced AC signal is then demodulated so that a DC voltage that is sensitive to the amplitude and phase of the AC signal is produced. Procedure: BEEE Lab 38 KCT College of Engg. & Tech. Department- AS 1. Connect the LVDT with the micrometer. 2. Connect the Voltmeter with the LVDT signal conditioner. 3. Connect the LVDT signal conditioner with the power supply of 110 Volts. 4. Set the position of LVDT such that a range of voltage from +10 to -10 volts can be achieved. 5. Change the LVDT displacement and record the voltmeter reading in the table. 6. Plot the graph voltage versus displacement. Table 1 S. No. Displacement (inch) 1 a= Resultant Displacement (x-a) (inch) Voltage (Volts) 2 3 4 5 6 7 8 9 10 11 12 13 BEEE Lab 39 KCT College of Engg. & Tech. Department- AS EXPERIMENT NO 14 Title: To study the working of thermocouple Objectives: To examine the thermocouple voltage and find corresponding temperature under the following conditions: 1. To measure voltage of thermocouple without considering the intermediate thermocouple effect of measurement setup. 2. To measure voltage of thermocouple with ice-point reference junction and fine corresponding voltage using the thermocouple table. 3. To measure voltage of thermocouple using ambient reference block and calculate the corrected voltage and then find the corresponding temperature. Apparatus: J type thermocouples 4-1/2 digit DVM. Temperature Indicator. Ice point water Boiling water Theory Thermocouple: Thermocouples plays very important role in industry. They are used as transducers to produce electromotive force to actuate equipment. They are used directly in such devices as furnace valves, recorders, and temperature-recording instruments. The simplest electrical temperature-sensitive device is the thermocouple. It consists of a pair of wires of dissimilar metals joined together at one end. The other ends are connected to an appropriate meter or circuit. The joined ends are known as the hot junction and the other ends are the cold ones. When the hot junction is heated, a measurable voltage is generated across the cold ends. With proper selection of the wires, the voltage varies in relationship to the temperature BEEE Lab 40 KCT College of Engg. & Tech. Department- AS being measured. Because of this, the thermocouple can be considered a thermoelectric transducer because of its characteristic of converting thermal energy into electrical energy. Figure 1 shows a typical circuit using a thermocouple to record temperature changes in a heat chamber. When the thermocouple is heated at the hot junction, while the cold junction is at a relatively constant temperature, the difference in temperature of the two junctions causes the meter to indicate a current. The indication of the meter is calibrated to be proportional to temperature. Procedure: 1. Setup the experiment as Figure 4 in theory sheets and measure voltage V. V = _____________________ T = _____________________ 2. Setup the experiment as Figure 6 of theory sheets and measure voltage V and calculate V1. Find temperature (T1) corresponding to V1 from table. V V1 V2 V (T1 T2 ) where, V1 t1 V2 t 2 t ( 0 C ) T ( 0 K ) 273.15 V V1 T T1 3. Setup the experiment according to figure 12. BEEE Lab 41 KCT College of Engg. & Tech. Department- AS a. Note reference temperature, which will be ambient temperature from temperature indicator. b. Measure V and find V1. V V1 TREF c. Find the temperature from table corresponding to V. TREF V V1 T T1 4. Compare voltages from setup 1, 2 and 3 and write your conclusions below. Conclusions: Explain: Which set up gives the correct temperature? Which set up gives maximum error? BEEE Lab 42 KCT College of Engg. & Tech. Department- AS EXPERIMENT NO 15 Title: To study the working of thermocouple Objectives: 1. To find the effect of loading on strain gauge resistance using Wheatstone bridge. 2. To find the effect of loading on strain gauge and find voltage difference using bridge circuit. 3. To find unknown load by using results and graphs obtained in part 1 and 2. Apparatus: Strain gauge Different Weights 1 kg, 2k, 5 kg. 4-1/2 digit DVM. Wheatstone bridge Three resistances of 120 ohms. Power supply Theory: The strain gauge is a transducer employing electrical resistance variation to sense the strain produced by a force or weight. It is a very versatile detector for measuring weight, pressure, mechanical force, or displacement. Strain, being a fundamental engineering phenomenon, exists in all matters at all times, due either to external loads or the weight of the matter itself. These strains vary in magnitude, depending upon the materials and loads involved. Engineers have worked for centuries in an attempt to measure strain accurately, but only in the last decade we have achieved much advancement in the art of strain measurement. The terms linear deformation and strain are synonymous and refer to the change in any linear dimension of a body, usually due to the application of external forces. The strain of a piece of rubber, when loaded, is ordinarily apparent to the eye. However, the strain of a bridge strut as a locomotive passes may not be apparent to the eye. Strain as defined above is often spoken of as "total strain." Average unit strain is the amount of strain per unit length and has BEEE Lab 43 KCT College of Engg. & Tech. Department- AS somewhat greater significance than does total strain. Strain gauges are used to determine unit strain, and consequently when one refers to strain, he is usually referring to unit strain. As defined, strain has units of inches per inch. Strain gauges work on the principle that as a piece of wire is stretched, its resistance changes. A strain gauge of either the bonded or the unbonded type is made of fine wire wound back and forth in such a way that with a load applied to the material it is fastened to, the strain gauge wire will stretch, increasing its length and decreasing its cross-sectional area. The result will be an increase in its resistance, because the resistance, R, of a metallic conductor varies directly with length, L, and inversely with cross-sectional area, A. Mathematically the relationship is R L A where is a constant depending upon the type of wire, L is the length of the wire in the same units as , and A is the cross-sectional area measured in units compatible with . Four properties of a strain gauge are important to consider when it is used to measure the strain in a material. They are: 1. Gauge configuration. 2. Gauge sensitivity. 3. Gauge backing material. 4. Method of gauge attachment. The sensitivity of a strain gauge is a function of the conductive material, size, configuration, nominal resistance, and the way the gauge is energized. Strain-gauge conductor materials may be either metal alloys or semiconductor material. Nickel-chrome-iron-alloys tend to yield high gauge sensitivities as well as have long gauge life. These alloys are quite good when used for dynamic strain measurements, but because of a high temperature coefficient, they are not as satisfactory for static strain measurements. Copper-nickel alloys are generally use when temperatures are below 500 to 600°F. They BEEE Lab 44 KCT College of Engg. & Tech. Department- AS are less sensitive to temperature changes and provide a less sensitive gauge factor than the nickel-chrome-iron alloys. Nickel-chrome alloys are useful in the construction of strain gauges for high temperature measurements. In using electric strain gauges, two physical qualities are of particular interest, the change in gauge resistance and the change in length (strain). The relationship between these two variables is dimensionless and is called the "gauge factor" of the strain gauge and can be expressed mathematically as: GF GF R L R L R R Strain In this relationship R and L represent, respectively, the initial resistance and the initial length of the strain gauge wire, while R and L represent the small changes in resistance and length which occur as the gauge is strained along with the surface to which it is bonded. The gauge factor of a strain gauge is a measure of the amount of resistance change for a given strain and is thus an index of the strain sensitivity of the gauge. With all other variables remaining the same, the higher the gauge factor, the more sensitive the gauge and the greater the electrical output. The most common type of strain gauge used today for stress analysis is the bonded resistance strain gauge shown below. BEEE Lab 45 KCT College of Engg. & Tech. Department- AS These gauges use a grid of fine wire or a constantan metal foil grid encapsulated in a thin resin backing. The gauge is glued to the carefully prepared test specimen by a thin layer of epoxy. The epoxy acts as the carrier matrix to transfer the strain in the specimen to the strain gauge. As the gauge changes in length, the tiny wires either contract or elongate depending upon a tensile or compressive state of stress in the specimen. The crosssectional area will increase for compression and decrease in tension. Because the wire has an electrical resistance that is proportional to the inverse of the cross-sectional area, R 1 , a measure of the change in resistance will produce the strain in the material. A Procedure: (A) Using Wheatstone bridge: 1. Connect strain gauge with Wheatstone bridge and find the resistance of strain gauge with no load and record the value in the table. 2. Find the resistance of strain gauge with loads, 1 kg, 2 kg, 3 kg, 4 kg and 5 kg, through Wheatstone bridge and record the values in the table. Load (kg) Resistance (ohms) 0 1 2 3 4 5 Unknown 3. Plot Resistance versus Load in the graph paper and write your conclusions. BEEE Lab 46 KCT College of Engg. & Tech. (B) Department- AS Using Bridge Circuit: 1. Connect strain gauge with the bridge circuit as shown the following figure. Set the power supply to 10 Volts and all three resistances are 120 ohms. R1 R2 V V s =10V a b DVM R3 Strain Gauge 2. Find the voltage difference ( V ) across nodes “a” and “b” using digital voltmeter (DVM) with no load and record the value in the table. 3. Find the voltage difference ( V ) using digital volt-meter (DVM) with loads, 1 kg, 2 kg, 3 kg, 4 kg and 5 kg, and record the values in the following table. Load (kg) V Voltage Difference (mV) 0 1 2 3 4 5 Unknown 4. Plot the voltage difference V versus Load in the graph paper and write your conclusions. (C) Find Unknown Load using Graphs: 1. Find the unknown load using resistance versus load graph (obtained in part A). BEEE Lab 47 KCT College of Engg. & Tech. Department- AS Unknown Load : _____________________ kg. 2. Find the voltage difference using voltage difference versus load graph (obtained in part B). Unknown Load : _____________________ kg. BEEE Lab 48 KCT College of Engg. & Tech. Department- AS EXPERIMENT Title: Full-Wave Rectification Objectives: To calculate and draw the DC output voltages of half-wave and full-wave rectifiers. Without smoothing capacitor and with smoothing capacitor Equipment: AC power supply or Function Generator 2 Voltmeters Function Generator Oscilloscope Components Diode: Silicon 4×(D1N4002) or Silicon Bridge rectifier Resistors: 10 kΩ, Capacitor :( 0.47 F) Capacitor :( 4.7 F) Electrolytic Capacitor :( 2×100 F) Fig. 5 1. Construct the circuit of Fig.5. Set the supply to 10 V p-p with the frequency of 50 Hz. Put the Channel 1 of the oscilloscope probes at function generator (trainer board) and sketch the input waveform obtained. Put Channel 1 of the oscilloscope probes across the resistor and sketch the output waveform obtained. Measure and record the DC level of the output voltage using the (Dc bottom in the C.R.O.) oscilloscope. Keeping the x-y button of the C.R.O. at outside position i.e. do not press it. Adjust the power supply unit at 10 V, then a sinusoidal or another type from function generator input voltage Vi will be displayed on the screen of the C.R.O. Measure the input signal voltage Vinput and the Voutput signal voltage Vo using both the voltmeter and C.R.O. V input = 10 volts BEEE Lab V (input) (Volt) VA (output) (Volt) 49 KCT College of Engg. & Tech. With voltmeter With oscilloscope Department- AS 10 Va.c Vp-p Vd.c VP-P Table 1 Draw the input waveform, Vi : and the output waveform, Vo : Calculate the effective value of the input signal V rms which is give by: Vrms = Vpp / (2√2) = Vm / √2 Transfer the graphs into a diagram , and determine the amplitude (peak value) V in and the frequency f of the Vin(t). Determine the amplitude and the frequency of the output voltage. The second of Kirchhoff's Laws is used to calculate the output voltage: VA (T) = V MAX INPUT – 2× 0.7 V V(th): threshold voltage across the diode for Si diode=0.7 V Smoothing and filtering Objectives Representing the ripple voltage on the load voltage Determining the ripple voltage as a function of the charging capacitor and the load resistor Measuring and calculating the r.m.s. value of the ripple voltage Fig. 6 BEEE Lab 50 KCT College of Engg. & Tech. Department- AS 1. Assemble the circuit as shown in Fig. 6 and apply an a.c. voltage 10 V, f = 50 Hz. 2. Use channel 1 of the oscilloscope to measure the voltage V o across the load resistor. 3. Record the settings of the oscilloscope: Y1 = --- volts/div (dc) t, X = --- ms/div. trigger switch to line. 4. Insert smoothing (filter) capacitor C = 0.47F, 4.7F,100 F; in the circuit to terminal parallel to the load one after other record the output voltage as shown in Fig.5, 5. determine the ripple voltage as a function of the charging capacitor and the load resistor 6. Connect an ammeter between terminals 1 and 3 in Fig.6 to measure the d.c. current. 7. Measure the d.c. component of the load current IL and the peak-to-peak value of the ripple voltage Vr pp for the combination of charging capacitor and load resistor as a function of the capacitance value of the smoothing capacitor C=0.47F, 4.7F, 100 F and at the same time measure the ripple voltage Vr pp using CRO and Record the values. 8. The r.m.s. value of the ripple voltage can be calculated using expression Vr ( rms ) I dc 2.4 I dc 2.4Vdc . C RL C 4 3 fC Where Idc in mA, C is in F, and RL is in k 9. Calculate the ripple frequencies for the values given in table 5 and enter your results into table 2. 10. Calculate the ripple factor r using the following equation: V (rms ) 1 1 r r ( ) Vdc 2 3 F R LC 11. Draw the output signal voltage in each case of using Cvalues. 12. Comment on the results you obtained. C (F) 0.47 4.7 V2 (voltmeter) (Volts) Vp-p (C.R.O. volts) I dc ( mA) T (msec) F = l/T (Hz) 100 BEEE Lab 51 KCT College of Engg. & Tech. Questions: Department- AS Table 2 1. Discuss the mechanism of operation of the Full-wave rectification using Si-bridge rectifier. 2. What do you notice from the values of the average output voltage in both; the half- and full wave rectification circuits? Comment. 3. Describe the ripple voltage dependence on the charging capacitor and the load resistor RL. 4. Is it possible to display both input and output voltages simultaneously with channel 1 resp. channel 2 give reasons for your answer in Full wave rectifier circuit (fig. 6) that you used? 5. Determine the peak reverse voltage across diode V 1in full wave rectifier circuit (fig. 6) that you used. BEEE Lab 52