A pair of parallel plates,forming a capacitor,are charged.The plates are pulled apart to triple the original separation,the charges on the plates remaining the same.What is the ratio of the final energy stored to the original energy stored?
A) 1/9
B) 1.5
C) 1/3
D) 3

Question

Quizplus · Accepted Answer

The energy stored in a capacitor is given by $ U = \frac{1}{2} \frac{Q^2}{C} $. When the separation between the plates is tripled, the capacitance $ C $ becomes one-third of its original value because $ C \propto \frac{1}{d} $. Therefore, the energy stored becomes three times the original energy, as $ U \propto \frac{1}{C} $.

A Pair of Parallel Plates,forming a Capacitor,are Charged