An electric dipole in a uniform electric field E experiences
A{'text': 'Zero net force but a torque of magnitude pE sin θ', 'label': 'A'}
B{'text': 'A net force with a corresponding restoring torque', 'label': 'B'}
C{'text': 'A finite non-zero force but zero net torque acting', 'label': 'C'}
D{'text': 'Neither a net force nor a net torque in any orientation', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': 'Zero net force but a torque of magnitude pE sin θ', 'label': 'A'}
1. In a uniform field, forces on +q and −q are equal and opposite.
2. Net force is therefore zero.
3. But the forces do not act along the same line, giving a torque.
4. Magnitude: τ = p × E × sin θ, where θ is the angle between p and E.
_Source: NCERT Class 12 Physics, Ch 1 "Electric Charges and Fields", §1.7_
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