Question

An electric dipole is along a uniform electric field If it is deflected by ${60}^{\circ },$ work done by agent is$2\times {10}^{-19}J$ . Then the work done by an agent if it is isdeflected by ${30}^{\circ }$ further is

• A. $2.5\times {10}^{-19}J$
• B. $2.0\times {10}^{-19}J$
• C. $4.0\times {10}^{-19}J$
• D. $2.0\times {10}^{-16}J$

Answer 1

The correct option is B $2.0\times {10}^{-19}J$

Working on electric dipole when deflected by an angle of ${60}^0$ is given by$,$

$W_1=U=-PE\cos {60}^0=-2\times {10}^{-19}J.$

Now$,$ work done in deflecting he dipole by another ${30}^0$ is given by$,$

$W_1=-PE\cos {90}^0=0$

Therefore work done by the agency which deflected dipole by ${30}^0$ mpore is$,$

$W=W_2-W_1=0-\left(-2\times {10}^{-19}\right)=2\times {10}^{-19}J.$

Hence,

option $\left(B\right)$ is correct answer.