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If a dipole of dipole moment \( \vec{p} \) is placed in a uniform electric field \( \vec{E} \), then torque acting on it is given by

1. \( \vec{\tau} = \vec{p} \cdot \vec{E} \)
2. \( \vec{\tau} = \vec{p} \times \vec{E} \)
3. \( \vec{\tau} = \vec{p} + \vec{E} \)
4. \( \vec{\tau} = \vec{p} - \vec{E} \)

Correct answer: \( \vec{\tau} = \vec{p} \times \vec{E} \)

Solution

The torque acting on a dipole in a uniform electric field is given by the vector cross product of the dipole moment \( \vec{p} \) and the electric field \( \vec{E} \), i.e., \( \vec{\tau} = \vec{p} \times \vec{E} \). This is because torque depends on the perpendicular component of the force acting on the dipole.

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