Lab 15 Series RL Circuits w prelab

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Algonquin College *

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9104

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Electrical Engineering

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Apr 3, 2024

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Lab 15, Series RL Circuits PRE-LAB Name NEELMANI BHARDWAJ__________ Date ___________________ Class ___________________ 1. What is Inductive Reactance, X L ? Show formula for X L . INDUCTIVE REACTANCE IS THE OPPOSITION FACEDBY THE CURRENT IN THE CIRCUIT DUE TO THE INDUCTOR PRESENT IN THE CIRCUIT . X L = 2x3.14xFxL 2. Does the Voltage Lead or Lag the Current in an inductor? Explain your answer VOLTAGE LEADS CURRENT BY 90 DEGREES IN AN INDUCTORBECAUSE OF AN INDUCTIVE LOAD , IT IS THE INDUCED ELECTOMOTIVE FORCE THAT HELPS THE CURRENT TO FLOW. 3. In a RL circuit, how does the Inductive Reactance manifest itself when a sinusoidal signal is applied? INDUCTIVE REACTANCE BEHAVE LIKE A OPPOSITION WHEN A SINE SIGNAL IS APPLIED TO IT. 4. In which quadrant are the voltage or impedance vector diagrams drawn and why? IT WILL BE IN THE SECOND QUADRANT BECAUSE VOLTAGE LEAD THE CURRENT BY 90 DEGREES. 5. In an RL circuit, does V R Lag or lead V S and why? V R lag Vs by 90 degrees because V r and curent are always in same phase . therefore, if source voltage leads the current by 90 so it will also lead resistor voltage by 90. Fall 2015 Lab 15 P a g e | 1

6. How does the phase angle in an RL circuit vary with Frequency? Explain your answer. If the frequency increases then X L increases and the total impedence of the circuit also increases . therefore phase angle also increases . AS phases angle = tan -1 (X L/ R) 7. How many methods are shown in this Lab for phase angle measurement in an RL circuit? Can you think of yet another method? Phase angle = tan -1 (X L/ R) 8. Can these methods be applied for a series RC circuit? Explain your answer? YES this method can als0 be applied to RC circuit but there will be Xc in place of X l. 9. Explain the basic approach of each method of step 9 (use back of page if you need more space). Fall 2015 Lab 15 P a g e | 2

10. What was the unit of τ in previous Labs? SECONDS 11. How long does it take for an RL circuit to fully react to a sinusoidal signal? 12. What happens to X L if the applied sinusoidal frequency increase to say infinity? AS THE FREQUENCY INCREASES THE IMPEDENCE OF THE INDUCTOR INCREASES AND OF CAPACITOR, IT DECREASES WHEN FREQUENCY IS TOO HIGH INDUCTOR START BEHAVING LIKE A CAPACITOR. Fall 2015 Lab 15 P a g e | 3

Lab 15 (eBook 24) Series RL Circuits Name ____________________ Date ___________________ Class ___________________ READING Text, Sections 12–1 through 12–3 OBJECTIVES After performing this experiment, you will be able to: 1. Compute the inductive reactance of an inductor from voltage measurements in a series RL circuit. 2. Draw the impedance and voltage phasor diagram for the series RL circuit. 3. Measure the phase angle in a series circuit using either of two methods. MATERIALS NEEDED One 10 kΩ resistor One 100 mH inductor REQUIRED LAB PREPARATION (PRELAB) 1.Read all sections of the lab. 2. Read the text book, sections 12-1 through 12-3 3. Find the required resistor and inductor for this lab as indicated in the Materials Needed section above 4. Review the differential probe measurement technique from Lab 8 5. Review the oscilloscope time “base operation” or what is called Horizontal Control depending on the oscilloscope manufacturer. 6. Complete the PreLab questions at the back of this document and place in teacher’s drop box before entering the Lab SUMMARY OF THEORY When a sine wave drives a linear series circuit, the phase relationships between the current and the voltage are determined by the components in the circuit. The current and voltage are always in phase across resistors. With capacitors, the current is always leading the voltage by 90°, but for inductors, the voltage always leads the current by 90° . (A simple Fall 2015 Lab 15 P a g e | 4

memory aid for this is ELI the ICE man, where E stands for voltage, I for current, and L and C for inductance and capacitance.) Figure 15–1(a) illustrates a series RL circuit. The graphical representation of the phasors for this circuit is shown in Figure 15–1(b) and (c). As in the series RC circuit, the total impedance is obtained by adding the resistance and inductive reactance using the algebra for complex numbers . In this example, the current is 1.0 mA, and the total impedance is 5 kΩ. The current is the same in all components of a series circuit, so the current is drawn as a reference in the direction of the x -axis . If the current is multiplied by the impedance phasors, the voltage phasors are obtained as shown in Figure 15– 1(c) . Figure 15–1 In this experiment, you learn how to make measurements of the phase angle. Actual inductors may have enough resistance to affect the phase angle in the circuit. You will use a series resistor that is large compared to the inductor’s resistance to avoid this error. PROCEDURE 1. Measure the actual resistance of a 10 kΩ resistor and the inductance of a 100 mH inductor. If the inductor cannot be measured, record the listed value. Record the measured values in Table 15–1 . 2. Connect the circuit shown in Figure 15–2 . Set the generator voltage with the circuit connected to 3.0 V pp at a frequency of 25 kHz. The generator should have no dc offset. Measure the generator voltage and frequency with the oscilloscope as many meters cannot respond to the 25 kHz frequency. Use peak-to-peak readings for all voltage and current measurements in this experiment. Component Listed Value Measured Value L 1 100 mH Fall 2015 Lab 15 P a g e | 5

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