Question

hat is the change in the potential energy of the system comprising the plates and the electron when the electron moves from the negative plate to the positive plate?

what is a

Answer 1

The potential energy of an electron in the electric field is given by

$$E_p=qV$$

When the electron moves from the negative plate to the positive plate its potential energy would change due changing of the potential of electric field

$$\Delta E_p=q\Delta V$$