Question

What orientation of an electric dipole in a uniform electric field corresponds to in stable and unstable equilibrium?

Answer 1

The potential energy of an electric dipole is given by

U= - pE cos (A)

For stable eqbm, energy must be minimum

So U should be - pE

So angle must be 0° as cos0=1

For unstable eqbm,energy must be max.

So U should be pE

So angle must be 180° as cos (180)=-1