A parallel-plate capacitor, with air dielectric, is charged by a battery, after which the battery is disconnected.A slab of glass dielectric is then slowly inserted between the plates.As it is being inserted:
A)a force repels the glass out of the capacitor
B)a force attracts the glass into the capacitor
C)no force acts on the glass
D)a net charge appears on the glass
E)the glass makes the plates repel each other

Question

Quizplus · Accepted Answer

As the glass dielectric is inserted between the plates, it reduces the electric field between them, which in turn reduces the energy stored in the electric field. This reduction in energy causes a decrease in the potential difference between the plates, which creates an overall net charge redistribution. This redistribution of charge creates an attraction force between the glass and the plates, pulling the glass into the capacitor. Therefore, the answer is B, a force attracts the glass into the capacitor.

A Parallel-Plate Capacitor, with Air Dielectric, Is Charged by a Battery