10-Mar-2015: Nodal analysis

Today, we continued our studies on nodal analysis. We employed what we learned about this topic by predicting the voltages across two different resistors and comparing them to the values that we found experimentally. We were also introduced to the concept of mesh analysis.

PRE-LAB

Figure 1: Application of nodal analysis

To begin our process, we calculated V1 and V2 by applying nodal analysis to the circuit shown in Figure 1. Since there are multiple variables called V1 and V2 in our work, the V1 and V2 we are referring to was circled in black.

PROCEDURES

Figure 2: Set-up of our circuit

After finding the theoretical values for V1 and V2, we constructed the circuit as shown in Figure 2. This set-up consisted of a 6.8 kΩ resistor, a 10 kΩ resistor, a 22 kΩ resistor, two 5 V voltage sources, and a 3 V voltage source.

Figure 3: Measured resistances

Next, we measured the actual resistances of each resistor. The measured values are shown in Figure 3.

Figure 4: Measured voltages

Finally, we turned on the voltage sources and measured the voltages across the 6.8 kΩ resistor and the 22 kΩ resistor. We labeled the voltage across the 6.8 kΩ resistor as V1 and the voltage across the 22 kΩ resistor as V2. The measured values are shown in Figure 4.

CONCLUSION

We found that our expected values and measured values were very different. In fact, the percent error for V1 was 454 percent. The reason for this enormous error can most likely be attributed to the fact that we carried out our calculations incorrectly. Another factor could have been that the set-up of our circuit was wrong.

Even though we were not able to find measured values that were close to the expected values, we still gained valuable experience in applying our knowledge about nodal analysis to an actual circuit.