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An electric dipole is placed in a uniform electric field. The resultant force acting on it is _______.

Asked in GSEB Board July 2018 · Torque, energy and work done

• (1) always zero
• (2) never zero
• (3) dependent on the relative position (orientation)
• (4) dependent upon the dipole moment

Step-by-step solution

Why the other options are wrong

• (2) In a uniform field the forces +q⃗E and -q⃗E are always equal and opposite, so their sum is zero for every orientation; only the torque can be non-zero.
• (3) Orientation changes only the torque, pE sin θ. The two forces stay equal and opposite at every angle because the field is the same at both charges.
• (4) A larger dipole moment gives a larger torque, not a net force: q⃗E + (-q)⃗E = 0 whatever the charge or the separation.

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