When an electric dipole is placed in a uniform electric field making angle `theta` with electric field, it experiences a torque `tau`. Calculate the minimum work donein changing the orientation to `2 theta`.

Explanation

`tau = pE sin theta`
`implies pE = ( tau)/( sintheta)`
`W = Delta U = - p E cos theta _(2) + p E cos theta_(1)`
`implies W = p E[cos theta -cos 2theta ]` `( :' theta_(1) = theta , theta _(2) = 2 theta )`
`=impliesW = ( tau)/( sin theta ) [cos theta - cos 2 theta ]`