The charge on an isolated capacitor does not change when a sheet of glass is inserted between the capacitor plates, and we find that the potential difference decreases (because the electric field...

The charge on an isolated capacitor does not change when a sheet of glass is inserted between the capacitor plates, and we

find that the potential difference decreases (because the electric field inside the insulator is reduced by a factor of 1/K).

Suppose instead that the capacitor is connected to a battery, so that the battery tries to maintain a fixed potential difference

across the capacitor.

(A) A light bulb and an air-gap capacitor of capacitance C are connected in series to a battery with known emf. What is

the final charge Q on the positive plate of the capacitor?

(B) After fully charging the capacitor, a sheet of plastic whose dielectric constant is K is inserted into the capacitor and

fills the gap. Does any current run through the light bulb? Why? What is the final charge on the positive plate of

the capacitor?