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 (K = 2.8) is inserted between the plates. Find the amount by which the potential difference across the plates changes.
C2 = KC1
q = CV
The Attempt at a Solution
I know that the charge will stay the same and voltage will drop.
I have no idea how to set this up mathematically. This is where I have hit a road block.