Question

A unit positive charge is moved along the circumference of a circle due to the attraction of a $-100$C charge at the centre of the circle. Then the work done in the process is _____.

• A. negative work of $100$ J
• B. positive work of $100$ J
• C. zero
• D. $\frac{Q.1}{4\pi {ϵ}_{0}r}$

Answer 1

The correct option is C zero

The force on the charge$\left(Q\right)$ due to $100C$ chagre at center is along the radius of the circle and the charge $Q$ is moved along the circumference and hence its displacement is always along the tangent to the radius at any point.

$W=\int \overrightarrow{F}.\overrightarrow{dr}=0$ since $\overrightarrow{F}$ and $\overrightarrow{dr}$ are normal to each other.

Answer-(C)