Question

how does a dipole kept in an electric field move

Answer 1

Under I deal conditions, wherein the length of dipole is very small, it will experience zero force,if it us aligned along the electric field.

If it's longitudinal axis is at some angle to the field, it will experience a torque acting on it.

If the the magnitude of the field changes along length of dipole, some force is also experienced.

Answer 2

When a dipole is kept in an uniform electric field...
the net force on it is zero but a net torque acts on it.. therefore it performs rotational motion,
when it is kept in an uniform external electric field..

Now, If the external electric field is not uniform,
then, besides torque a net force also acts on the dipole, therefore it performs a combination of rotational and transnational motion altogether..

Hope it helps...