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

Asked in GSEB Board July 2016 · Torque, energy and work done

• (1) depends on its relative position
• (2) is always zero
• (3) is never zero
• (4) depends on its dipole moment

Step-by-step solution

Why the other options are wrong

• (1) In a uniform field ⃗E is the same everywhere, so moving or turning the dipole does not change the two forces +q⃗E and -q⃗E: they always cancel. Orientation changes the torque, not the net force.
• (3) The forces on the two charges are equal and opposite in a uniform field, so their sum is always zero. It is the torque, not the force, that is generally non-zero.
• (4) A bigger dipole moment means a bigger couple, not a net force: p enters the torque pE sin θ, while the two forces ± q⃗E still cancel exactly.

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