## Lab 6 – Thevenin Equivalent Circuits

Part 1. Black Box Testing to Determine the Thevenin
Equivalent Circuit
1. Use Multisim Live to build the circuit above. Connect a voltmeter across the output
terminals, a and b. Directly measure Voc to determine Vth.
1. Voc = Vth =
2. Connect a 1M? load resistor across the output terminals. Save a copy of your
schematic and include with your lab write-up. Measure and record VL.
1. VL =
3. How does this value compare to your measurement of Voc from above? What do you
think is the reason for that relationship?
4. Now adjust the values of the load resistance according to the table below. Measure
and record VL and IL as you go. Compute Power = VL * IL
RL VL IL Power= VL * IL
1M?
100k?
10k? 8.1633 V 816 uA 6.661 mW
2.5k?
2k?
1.5k?
1k? 3.3058 3. 3058 mA 10.92 mW
5. Maximum power transfer occurs when the load resistance is equal to Rth. Which load
resistance gave you the maximum power?
RL, max power =
6. Next, measure Isc = Short circuit current. Disconnect the load resistor and attach an
ammeter directly to the output terminals of the black box to measure Isc.
Isc =
7. Compute Rth based on Voc and Isc.
Rth = Voc/Isc =
How does your Rth compare to the RL value that gives max power?
8. A. Connect a load resistor equal to Rth and to the output terminals of the circuit.
Measure the load voltage and current and compute the power delivered to the load.
VL=
IL =
P =
B. Repeat the measurements above for a resistor half as large as RTH.
VL=
IL =
P =
C. Repeat the measurements above for a resistor twice as large as Rth.
VL =
IL =
P =
9. How do the values for (8a), (8b), (8c) compare?
Part 2. Lab Report
Write or type all of your calculations and answers to the questions above and save as