Day 8: Thevenin's Theorem

Thevenin's Theorem

Thevenin’s theorem states that a linear two-terminal circuit can be replaced by an equivalent circuit consisting of a voltage source V

_Th in series with a resistor R_Th , where V_Th is the open-circuit voltage at the terminals and R_Th is the input or equivalent resistance at the terminals when the independent sources are turned off.

Here in our first problem we were finding the Thevenin resistance and voltage through the middle lead (That is shown as a break in the circuit). We were able to find the equivalent resistance to find the Thevenin resistance. When the power sources were put back in, we were able to use source transformations to easily find the Thevenin voltage of the circuit.

Thevenin's Theorem Lab
In this lab, we experimentally investigate Thevenin’s Theorem. We will analytically determine a Thevenin equivalent for a given circuit; we will then experimentally determine the Thevenin resistance and the open-circuit voltage necessary to create the Thevenin equivalent circuit.

For the prelab, we were instructed to find the Thevenin resistance and voltage of the circuit. Taking out the power sources, the resistance was easy enough to find. Using Mesh analysis, finding the Voltage came out fairly easily.

Here we checked our work using EveryCircuit. (And, Bonus, you also get my Outfit of the day: Red Trader Joe's Hawaiian Shirt).

Two pictures of our circuit. A much easier circuit to set up than the previous few circuits. 

Not only was the circuit easy to set up, but we were able to get pretty good data from it! Here we are measuring to find the Thevenin Voltage. Very close to our estimate of 54 microvolts. 

After finding experimental data using the given circuit, we used a 10K Pot to find the voltage and the power given resistance values of 0K - 10K ohms. We found that our Pot only went up to a max of 8.7K ohms. Above are the values we procured.

When graphed on excel, we found that the best fit we could get was a quadratic quadratic function. Logarithmic didn't fir very well. This is the best we could get.