24-Mar-2015: Non-ideal Power Sources/Maximum Power Transfer

Non-ideal Power Sources

PURPOSE

PRE-LAB

Figure 1: Expected values of Vout, Is, and P

Before conducting our experiment, we determined the expected values for the measured voltage (Vout), source current (Is), and the power dissipated by the resistor (P). We calculated these values for both an ideal voltage source (right) and a non-ideal source (left). The work is shown above in Figure 1.

PROCEDURES

Figure 2: Set-up of circuit

Figure 3: Measured values of Vout and R

Figure 2 shows the actual set-up of the circuit. After setting up our circuit, we turned on the voltage source and made sure that it was actually outputting 1 V with our multimeter. Then, we applied the voltage onto the circuit and measured the Vout. We repeated this process for three different resistors. The measured values are displayed above in Figure 3, including the actual resistances of the resistors.

Figure 4: Measured (Vout and R) and calculated (Rs, Is, and P) values

From these measured values, we calculated the internal resistance of the voltage source by using the formula shown earlier in Figure 1. We also found the source current and the power dissipated by the resistor for each trial. The resulting values are illustrated in Figure 4. 

CONCLUSION

From looking at the values in Figure 4, we noticed that the internal resistance of the voltage source decreased as we increased the resistance value of the resistor in our circuit. One of the possible reasons that we think that this may have occurred is because the higher resistance values made the internal resistance more and more negligible.