Question

A parallel–plate capacitor is connected to a battery. Without disconnecting the capacitor, a student pulls the capacitor’s plates apart so that the plate separation doubles. As a result of this action, what happens to the voltage across the capacitor and the energy stored by the capacitor?

(A) the voltage doubles; the energy stays the same

(B) the voltage halves; the energy doubles

(C) the voltage doubles; the energy halves

(D) the voltage stays the same; the energy halves

(E) the voltage stays the same; the energy doubles

Answer 1

The correct option is: (D) the voltage stays the same; the energy halves

Explanation:

Since the battery remains connected, V remains constant. C decreases as d increases (C ∝ 1/d) and U_C = ½ CV²