A dipole is placed in a non-uniform electric field as shown. In which direction will it move?

Solution & Explanation

Answer: (d) Solution: In a non-uniform electric field the two charges of the dipole experience unequal forces, so there is a net translational force in addition to any torque. A dipole always tends to move toward the region of stronger field, because doing so lowers its potential energy U = −p·E (the field magnitude is larger there once the dipole is aligned). From the figure, the stronger field (and lower PE) lies to the right, so the dipole moves toward the right as its potential energy decreases. Hence option (d).