3/28 Thevenin's Theorem

We started with a circuit and used Everycircuit to find the value of the current through RL. The picture below was the circuit we drew in Everycircuit.


After that, we did a problem by using Thevenin's Theorem, but I forgot to take a picture...
Then we did out lab for today.

Thevenin’s Theorem


The picture above is the calculated Rth and Vth for this circuit. We got Rth = RL =7.7k ohms and Vth = 0.46V.
Resistance error:
1k(0.96k), 2.2k(2.15k), 4.7k(4.6k), 6.8k(6.68k), 1.8k(1.74k), 6.8k(6.68k)


The picture above is the basic set up for this lab without power supply.

The measured value for the Thevenin resistance is 7.4kohms, comparing to the calculated value (7.7kohms), the % error is 3.90%.
To measure the Thevenin voltage, we need to apply voltage source.

The picture above is the basic set up for the circuit with power supply.

The measured value for Thevenin voltage is 0.448V, comparing to the calculated value (0.46V), the % error is 2.60%.

For part three, we chose a 4.5k ohms resistor as our load resistor, and we calculated that the voltage across the load will be 0.187V.
From our measurement, we got 0.165V. The % error is 11%.
The reason why it is not very precise is because the value of the resistors are different than the actual values of the resistors.

For part four, we used the potentiometer to create the measured values of thevenin resistance (7.2ohms), and then, we supplied the circuit with 0.488V.
We used the same resistor that we used in part three (4.5k ohms) into the circuit, and we got the voltage drop is 0.167V, comparing this value to what we calculated, the % error is 1.1%.


The maximum resistance that the potentiometer can create is 8.5k ohms, so we cannot graph a bell curve that we expected.

Summary

We leaned about how to use Thevenin's Theorem and how to apply it to a real circuit. The lab proves that Thevenin's Theorem is a pretty uesful tool to analyze the circuit and to create a much simpler circuit that has the same function. Also, we knew how to find the maximum power dissipated by the load when the RL=Rth.