Question

A dipole is placed in an electric field such that the axis of the dipole is parallel to the electric field. The torque acting on the dipole will be the maximum in this case. The statement is _____

(a) True

(b) False

I got this question in an online quiz.

I want to ask this question from Dipole in a Uniform External Field topic in division Charges and Fields of Physics – Class 12

Answer 1

Right answer is (b) False

To elaborate: We know, the torque acting on a dipole of moment p and placed in a field E is equal to \(\vec{p} \times \vec{E}\) which can also be written as p*E*sinθ following the cross product rule. In this case, the field is parallel to the axis of the dipole. Therefore θ=0 and sinθ is also equal to 0. Hence, the torque acting on the dipole will be the minimum i.e. 0. The torque will be maximum if θ=90 degree and so sinθ becomes 1 in that case.