20. If a dipole of dipole moment p is placed in a uniform electric field E, then torque acting on it is given by ?

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

<p>(a) \( \vec{\tau} = \vec{p} \cdot \vec{E} \)</p>

<p>(b) \( \vec{\tau} = \vec{p} \times \vec{E} \)</p>

<p>(c) \( \vec{\tau} = \vec{p} + \vec{E} \)</p>

<p>(d) \( \vec{\tau} = \vec{p} - \vec{E} \)</p>

Answer :  <p>(b) \( \vec{\tau} = \vec{p} \times \vec{E} \)</p>