# Torque ( electric dipole ) problem

We all know that every object tries to be in a minimum energy state, for example if we take a spring and compress it we increase its potential energy and now if we release it all that energy gets converted into the kinetic energy, so following the same reasoning see if I take an electric dipole and align it so that it's dipole moment is antiparallel to the electric field, it would have highest potential energy and I would have to do work to bring it to that position, now if I release it it should come back to its minimum energy state(if not please tell why), but see torque is given by $\vec{p} \times \vec{E}$, now angle between them is $\pi$ radian and the torque is $0$, so would it stay at that high energy state forever without coming back to its low energy state?

• It would be in unstable equilibrium. If nothing disturbs it at all, then yes, theoretically it will stay in that state. – GeeJay Mar 13 '17 at 12:07

Yes. Classically, (as mentioned by garyp) it would stay in that position forever if the angle between the electric field vector and the dipole moment is the exactly $\pi$ radians. The dipole is in unstable equilibrium, so a slight change in position will cause it to align with the electric field, thus decrease its potential energy.