Question

In each situation of column-I, two electric dipoles having dipole moments vector p₁  and p₂  of same magnitude (that is, p₁ = p₂ ) are placed on x-axis symmetrically about origin in different orientations as shown. In column -II certain inferences are drawn for these two dipoles . Then match the different orientations of dipoles in in column-I with the corresponding results in column-II and indicate your answer by darkening appropriate bubbles in the 4 × 4 matrix given in the OMR.

Column-I	Column-II
perpendicular to x-axis as shown)	(p) The torque on one dipole due to other is zero.
perpendicular to x-axis as shown)	(q) The potential energy of one dipole in electric field of other dipole is negative
parallel to x-axis as shown)	(r) There is one straight line in x-y plane (not at infinity) which is equipotential
parallel to x-axis as shown)	(s) Electric field at origin is zero.
	(t) The force one dipole due to other is non zero

Answer 1

(A) -p,r, t ; (B)  - p,q,s,t ; (C)  - p,q,r,t ; (D)  - p,s,t

(Moderate)The electric field due to one dipole at centre of other dipole is parallel to that dipole. Hence torque on all given dipoles is zero. In case B and C the electric field at second dipole due to first is along the second dipole. hence electrostatic potential energy of second dipole is negative. In case A and B x-axis is line of zero potential. In case B and C electric field at origin is zero.