ENGR225  Circuit Analysis                                              Name_________________________

Lab #5 - Capacitors and Inductors                                        Date__________________________

 

Objectives:

 

To see examples of capacitors and inductors and to see how they are specified.

To verify the way capacitors and inductors combine in series and in parallel.

To verify the V-I relationship for capacitors and inductors.

To understand better how capacitors and inductors respond to dc voltages and currents.

 

Procedures:

 

1.  Observe the examples of capacitors and inductors offered in the lab.  Discuss how a capacitor and an inductor are rated or specified.  What range of capacitances and inductances do we have in the lab?  Compute the energy stored in the largest capacitor and the largest inductor when operating at their rated voltage or current, respectively.

 

2.  Use the RLC meter to measure the inductance of two inductors individually and then in series and in parallel.  Repeat for two capacitors.  Calculate the expected series and parallel equivalents and compare with the measured values.  Also, measure the resistance of the inductors and capacitors with the LCR meter and with the ohmmeter of your DMM.  (Remember to first zero your ohmmeter with the leads connected to each other before measuring on the 20Ω scale.)

 

3.  Hook up Circuit A shown on the next page.  Use the oscilloscope to measure V1 and Vc simultaneously one above the other.  Include the waveforms in your report labeling the traces, the times, and the amplitudes.  Use the hints with the schematic to show that the expected V-I relationship for the capacitor (i=Cdv/dt where dv/dt is the slope of the voltage curve) was obtained.

 

4.  Hook up Circuit B shown on the next page.  Note the change in frequency.  Again measure V1 and VL and sketch them in your report.  Label times and amplitudes.  Again use the hints with the schematic to show that the expected V-I relationship for this inductor (v=Ldi/dt where di/dt is the slope of the current curve) was obtained.

 

5.  Change the resistor to 1kΩ in Circuit B and change the Wavetek frequency to 200 Hz. Sketch V1 and VL as before.  Explain the V-I relationship that you see!  As a hint remember that in part 2 you found that inductors can be represented by two ideal components.

 

6.  Refer to the Circuit C.  Calculate the expected values for V1 and V2 across the two capacitors.  Then build the circuit and measure these two voltages.  Compare your measurements with the calculated values.  Summarize in words how you treat capacitors and inductors in dc circuits (circuits with only dc sources).

 


 

Circuit A

Note: VR = V1-VC ≈ V1 (since V1 >> VC)

 

        So i = VR/R ≈ V1/R = iC (cap current)

 

 

 

 

 

 

Circuit B

Note: VR = V1- VL  V1 (since V1 >> VL)

 

       So i = VR/R ≈ V1/R = iL (ind current)

 

 

 

 

 

 

 

 

 

Circuit C