19-Mar-2015: Thevenin's Theorem

PURPOSE

The purpose of this lab was to apply our knowledge on Thevenin equivalent circuits in a real-world situation.

PRE-LAB

For the pre-lab, we analyzed the circuit shown in Figure 1 (click to enlarge), marked with the red circle. We found the open circuit voltage by examining the Thevenin equivalent circuit displayed in Figure 1 with the blue circle. We found this voltage to be 0.45 V. Then, we found the Thevenin resistance (Rth) by utilizing the circuit labeled with the green circle. We ended up with a value of 7.198 kΩ.

PROCEDURES

Figure 2: Set-up of our circuit

After finishing the pre-lab, we constructed the circuit as shown in Figure 2 above. We then proceeded to measure Thevenin resistance of the circuit (Figure 3). We found this value to 14.83 kΩ.

Figure 3: Measured Thevenin resistance

Percent error = (|expected value - measured value| ÷ expected value) x 100%

= (|7.198 kΩ - 14.830 kΩ| ÷ 7.198) x 100%

= (|-7.632| ÷ 7.198) x 100 %

= (7.632 ÷ 7.198) x 100 %

= (1.060) x 100 %

= 106.0 %

CONCLUSION

This experiment was a useful learning experience because it allowed us to implement what we learned during lecture in an actual experiment. This allows us to achieve a deeper understanding of the concepts that we learn in class.

When we measured the actual resistance of our Thevenin equivalent circuit, we found that the measured value was much bigger than the expected value. In fact, when we calculated the percent error, it was 106 percent. This is most likely due to two factors. The first possible reason for this error is that we made a mistake when performing the mathematical process. We could have taken the wrong steps when finding the value or we could have simply added wrong. The second factor that most likely caused this huge error is the fact that we could have set up the circuit incorrectly.