# Energy required to charge up a capacitor

1. Jun 12, 2012

### Maxwell1

The energy required to charge a capacitor is:

W = ½εrCV2

From this we see that a capacitor with a linear dielectric in between its plates requires a bigger energy to charge up to a given potential. My question is: Should this be intuitive?
My teacher said that it is because the parts of the electric field is cancelled off by the bound charges. I guess I can understand that since you then have to pull in more charge overall. However - wont these charges being pulled in also experience a weaker repulsion due to the cancelled off charges?

2. Jun 12, 2012

### Staff: Mentor

Welcome to the PF.

$$W = \frac{1}{2}C(V)V^2$$