An empty capacitor is connected to a 12.0 V battery and charged up. The capacitor is then disconnected from the battery, and a slab of dielectric material (dielectric constant "k" = 2.8) is inserted between the plates. Find the amount by which the potential difference accross the plates changes. Specify whether the change is an increace or a decreace.

7.71 V

Explanation:

When the charge remains constant, the potential difference decrease by the factor of the dielectric constant K

V new = V initial / K = 12 V / 2.8 = 4.29 V

ΔV ( change in potential) = V initial - V new ( after dielectric has been added) = 12 V - 4.29 V =      7.71 V

The potential difference decreases by 7.71 V

think about the oscillation of the toy shown in the video. when the toy is at the highest point of its motion, its velocity is zero and its acceleration is negative.