PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A circuit contains an ideal battery, a resistor of resistance R, and a parallel-plate capacitor whose capacitance can be varied by changing the distance between its plates. Starting with the switch open and the capacitor uncharged, the switch is closed, allowing the capacitor to charge through the resistor. The experiment is repeated with the plate separation increased so the capacitance is larger. Compared with the first trial, which statement best describes how the charging process changes?
(a) The initial current is larger because the larger capacitance presents less opposition to the battery.
(b) The shape of the charging curve is unchanged because only the resistance controls the time dependence.
(c) The time required for the capacitor to reach half of its final voltage increases.
(d) The time required for the capacitor to reach half of its final voltage decreases because the larger capacitance stores charge more quickly.