Chapter 21, Problem 86GP

CE Predict/Explain (a) When the switch is closed in the circuit shown in Figure 21-57, does the total power dissipated in the circuit increase, decrease, or stay the same? (b) Choose the best explanation from among the following:

1. I.        Closing the switch adds one more resistor to the circuit. This makes it harder for the battery to supply current, which decreases the power dissipated.
2. II.      The equivalent resistance of the circuit is reduced by closing the switch, but the voltage remains the same. Therefore, from P = V²/R we see that the power dissipated increases.
3. III.   The power dissipated remains the same because power, P = IV, is independent of resistance.

Figure 21-57

Problems 85 and 86