An electric dipole of moment p is placed in a uniform electric field E, with P parallel to E. it is then rotated by an angle q. The work done is

Explanation

Let AB be a electric dipole having charges -q and +q
Electric dipole moment of AB = p
Electric field = E
The workdone by a dipole, when it is rotated through an angle q from E,
`W = int_(0)^(q) pE sin theta d theta`
`implies W = pE [cos theta]_(0)^(q) = pE (cos 0^(@) - cos q)`
`:. W = pE (1 - cos q)`