Consider a permanent dipole of dipole moment p in a non-uniform elect…

The correct answer is Option (3) → The direction of net force is in the direction of increasing electric field when \( \vec{E} \) is parallel to \( \vec{p} \).

In a non-uniform field the two charges \( +q \) and \( -q \) of a dipole sit in fields of different strength, so the forces \( +q\vec{E} \) and \( -q\vec{E} \) do not cancel.

Let the field increase along \( +x \).

Dipole moment parallel to the field: the positive charge is the one further along \( +x \), in the stronger field. The force \( +qE \) on it is larger than \( qE \) on the negative charge in the opposite direction, so the net force points along \( +x \), the direction of increasing field.

Dipole moment anti-parallel to the field: now the negative charge is in the stronger field, and the larger force \( -qE \) points along \( -x \), so the net force is towards decreasing field.

Options (1) and (2) — Incorrect. The net force is along the direction in which the field changes, not perpendicular to it.

Option (4) — Incorrect. For the anti-parallel case the net force is towards decreasing field.

NCERT (2026-27):
Dipole in a Uniform External Field – “… In either case, the net torque is zero, but there is a net force on the dipole if E is not uniform. Figure 1.20 is self-explanatory. It is easily seen that when p is parallel to E, the dipole has a net force in the direction of increasing field. When p is antiparallel to E, the net force on the dipole is in the direction of decreasing field.”