A parallel-plate capacitor is charged to by a battery and then disconnected

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

A parallel-plate capacitor is charged to

24\,\text{V}

by a battery and then disconnected, leaving the charge isolated on the plates. The plate separation is subsequently tripled, and a dielectric with constant

\kappa = 4

is fully inserted between the plates. By what factor does the electric potential energy stored in the capacitor change? (a) It increases to

\dfrac{4}{3}

of its original value. (b) It decreases to

\dfrac13

of its original value. (c) It decreases to

\dfrac34

of its original value. (d) It increases to 3 times its original value.

Related theory

Capacitance
Energy Stored in Capacitors
Effect of dielectric on capacitance
Electrostatic Potential and Capacitance

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