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An electric dipole is placed in a non-uniform electric field. Then

Asked in GUJCET 2019 · Torque, energy and work done

• (1) the resultant force acting on the dipole is always zero
• (2) the torque acting on it may be zero
• (3) the resultant force acting on the dipole may be zero
• (4) the torque acting on it is always zero

Step-by-step solution

Why the other options are wrong

• (1) That holds in a uniform field. In a non-uniform field the two charges sit in fields of different strength, so q⃗E₊ and -q⃗E₋ do not cancel.
• (3) The 'may be zero' belongs to the torque. In a non-uniform field the field at +q differs from the field at -q, so the two forces do not cancel and the dipole feels a net force - as NCERT puts it, in a non-uniform field the net force is non-zero.
• (4) The torque ⃗p×⃗E vanishes only when ⃗p lies along the field; in any other orientation the dipole is twisted.

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