Chapter 25, Problem 70P

Aslab of copper of thickness b = 2.00 mm is thrust into a parallel-plate capacitor of plate area A = 2.40 cm ² and plate separation d = 5.00 mm, as shown in Fig. 25-57; the slab is exactly halfway between the plates, (a) What is the capacitance after the slab is introduced? (b) If a charge q = 3.40 μC is maintained on the plates, what is the ratio of the stored energy before to that after the slab is inserted? (c) How much work is done on the slab as it is inserted? (d) Is the slab sucked in or must it be pushed in?

Figure 25-57 Problems 70 and 71.