A dipole moment p is kept along an electric field E such that E and p are in the same direction. Find the work done in rotating the dipole by an angle of π:
Correct answer: A. W = 2Ep
- A. W = 2Ep
- B. W = -2Ep
- C. W = Ep
- D. W = -Ep
Explanation
The potential energy of a dipole in an electric field is given by U = -pE cos θ. Initially, the dipole is aligned with the field, so θ1 = 0° and U1 = -Ep. After rotating by π, θ2 = 180°, making U2 = Ep. The work done, W, is the change in potential energy: W = U2 - U1 = Ep - (-Ep) = 2Ep. Thus, the correct answer is W = 2Ep. The other options are incorrect as they do not account for the proper calculation of the potential energy difference.
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