Question

Find the force interaction between the ring and infinite line charge kept along the axis of the ring.

• A. $\frac{k\lambda Q}{r}$
• B. $\frac{\sqrt{2}k\lambda Q}{r}$
• C. $\frac{2k\lambda Q}{r}$
• D. Zero

Answer 1

The correct option is D Zero

Considering two symmetrically placed small line charge element on the ring.
The force $\left(dF\right)$ due to it on the infinite line charge is shown in the figure.


From the figure, we can see that all the force components along $y-$ direction cancels each other by symmetry.

Similarly, force components along $x-$ directions also cancel each other.

Therefore, net force of interaction of the system is zero.

So, option $\left(d\right)$ is correct.