How does the energy change in a capacitor with variable plate distance?

[chopticks]

Homework Statement

A capacitor has variable distance between the plates . It charges with a constant charge Q and the distance between the plates increase with 20%. How many percent does the energy change in the electric field between the plates?

Homework Equations

E = (1/2)QV = (1/2)CV^2 = Q^2/2C

The Attempt at a Solution

I remember my teacher said that the energy only depends on e. So the energy is the same.

 

[azatkgz]

Homework Equations

E = (1/2)QV = (1/2)CV^2 = Q^2/2C

Here Q is constant.Becuase distance between the plates changes,capacitance also changes.

C=\epsilon\frac{A}{d}

\epsilon and A are also constants.

 

[chopticks]

ok. If I want to find the maximum energy/volume then the distance doesn't matter, right?