Chapter 24, Problem 24.71P

DATA You are conducting experiments with an air-filled parallel-plate capacitor. You connect the capacitor to a battery with voltage 24.0 V. Initially the separation d between the plates is 0.0500 cm. In one experiment, you leave the battery connected to the capacitor, increase the separation between the plates, and measure the energy stored in the capacitor for each value of d. In a second experiment, you make the same measurements but disconnect the battery before you change the plate separation. One set of your data is given in Fig. P24.71, where you have plotted the stored energy U versus l/d. (a) For which experiment does this data set apply: the first (battery remains connected) or the second (battery disconnected before d is changed)? Explain. (b) Use the data plotted in Fig. P24.71 to calculate the area A of each plate, (c) For which case, the battery connected or the battery disconnected, is there more energy stored in the capacitor when d = 0.400 cm? Explain.

Figure P24.71