Lab Report Day Eight - Thevenin's Theorem

At first, we start a lab stimulation with EveryCircuit.

We then do a pre-lab, using EveryCircuit to see if we get the right answer.

The Thevenin resistance is 7.349 k ohm, and the open-circuit voltage is 0.456 V. 

 

This is a sketch our replaced Thevenin’s Theorem.

 

This is the circuit we stimulate form EveryCircuit.

 The purpose of this lab is to use experiment to see how Thevenin’s Circuit works, and compare to the complex circuit. 

At first, we measure the true value of our resistor that we are going to use in the circuit. 

 

 

 This is the set up of this experiment when it is in complex form.

 We measure the voltage across the 4.7 K resistor to be 0.179 V. Our theoretical value is 0.175 V. The precent difference is -2.29%. 

 

 We measure the voltage across the 1 K resistor to be 0.055 V. Our theoretical value is 0.055 V. The precent difference is 0%. 

 This is the circuit replaced by Thevenin’s Theorem. It is much simpler. We use three resistors in series to replace the 7.35 k ohm resistor.

 We measure the voltage across the 4.7 K (actual value 4.57 k) resistor to be  0.175 V. Our theoretical value is 0.175 V. The precent difference is 0%. We can see that when we use less elements with Thevenin’s Theorem, we can get a more accurate value.

The summary of our data table. 

Then, we use a potentiometer to replace the load resistor. It can provide various resistance . We measured the resistance of the potentiometer, and record the voltage across it. 

This is the set up of the circuit.

 

 Here is a summary table of our results. 

 We put the data in EXCEL. We get our maximum power to be 7.1225*10^-6 W, when the load resistance is 6490 ohm. 

Here is a graph of the Power vs. Resistance graph. We can see it is approximately a straight line. So we can say that the power of the load resistor can be considered constant. And we calculate the average value of the power, which is about 6.8442*10^-6 W. 

 

Summary:

In today’s lab, we practice more on Thevenin’s Theorem, have better understanding of Thevenin’s Theorem, and build circuits using Thevenin’s Theorem. We can see that since the Thevenin’s Circuit is much simpler. Thus, it will be more accurate on the results. Also, based on our experiment, we can see that the power of a load resistance is about constant. It will only change a little bit when the resistance changes.