Question

A ring of diameter d is rotated in a uniform electric field until be position of maximum electric flux is found. The flux is found to be $\varphi$. If the electric field strength is $E=\frac{X\varphi }{\pi d^2}$. Find out X ?

Answer 1

flux will be maximum when the plane of the ring is perpendicular to the uniform field.
Then,
$\varphi =EA\Rightarrow \varphi =E\frac{\pi d^2}{4}\Rightarrow E=\frac{4\varphi }{\pi d^2}$