Question

An electric dipole is along a uniform electric field: If it is deflected by $60^\circ$, work done by an agent is $2 \times 10^{-19}$ Then the work done by an agent if it is deflected by $30^0$ further is

• A. $2.5 \times 10^{-19}$ J
• B. $2 \times 10^{-19}$ J
• C. $4 \times 10^{-19}$ J
• D. $2\times 10^{-16}$ J

Answer 1

Answer: (B)

Working on electric dipole when deflected by an angle of $60^{\circ}$ is given by, $W _{1}= U =- PE \cos 60^{\circ}=-2 \times 10^{-19} J .$
Now, work done in deflecting he dipole by another $30^{\circ}$ is given by, $W _{1}=- PE \cos 90^{\circ}=0$
Therefore work done by the agency which deflected dipole by $30^{\circ}$ mpore is,
$W = W _{2}- W _{1}=0-\left(-2 \times 10^{-19}\right)=2 \times 10^{-19} J .$