A capacitor of capacitance C is charged by connecting it to a battery of emf epsilon. The capacitor is now disconnected and reconnected to the battery with the polarity reversed. Calculate the heat developed in the connecting wires.

Explanation

When the capacitor is connected to the battery, a charge Q = C epsilon appers on one plate and -Q on the other. When the polarity is reversed, a charge -Q appears on the first plate and +Q on the second. A charge 2Q, therfore,, passes through the battery from the nagative passes through the battery form the negative to the positive terminal. The battery does a work `
` W= (2Q)epsilon = 2 Cepsilon^2`
` in the process. The energy stored in the capacitor in the same in the two cases. Thus, the work done by the battery appears as heat in the connecting wires. The heat produced is, therfore, 2C epsilon^2.