A parallel plate capacitor has smooth square plates of side ''a''. It is charged by a battery so that, the charge density becomes `sigma`. After charging, the battery is disconnected. Now a smooth dielectric slab of length a which can fill the space between the plates is introduced between the plates from one side between the plates.
.

Options

A. The slab can execute `SHM` between the plates.
B. The plate can execute oscillatory motion which is not `SHM`
C. The magnitude of the force experienced by the slab is constant
D. The magnitude of the force experienced by the slab is not constant.

Answer

B, D

Explanation

Force on the slab is given by `F=(dU)/(dx)`, where `U` is slab in it. Here `F` is not directly proportional to `x`, but depends on `x`.