272254 An electric dipole of moment \(\vec{p}\) is placed normal to the lines of force of electric intensity \(\vec{E}\), then the work done in deflecting it through an angle of \(180^{\circ}\) is
\(\{\mathrm{d}\} \mathrm{W}=\mathrm{PE}\left(\cos 90^{\circ}-\cos 270^{\circ}\right)=0\).