A capacitor (Figure) is made of two conducting plates of area A separated in air by a

Question:

A capacitor (Figure) is made of two conducting plates of area A separated in air by a spacing x. The terminal voltage is v, and the charge on the plates is q. The capacitance C, defined as the ratio of charge to voltage, is where ?0 is the dielectric constant of free space (in SI units ?0 = 8.85 X 10-12 F/m).

a. Using the results of Problem 3.19, derive expressions for the energy Wild(q, x) and the co-energy Wfld (V, x).

b. The terminals of the capacitor are connected to a source of constant voltage V0. Derive an expression for the force required to maintain the plates separated by a constant spacing x = 8.