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
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).
