A ring of radius `R` is placed in the plane with its centre at origin and its axis along the `x-axis` and having uniformly distributed positive charge.A ring of radius `r( ltlt R)` and coaxial with the larger ring is moving along the axis with constant velocity then the variation of electrical flux `(phi)` passing through the smaller ring with position will be best represented by :

Options

A.
B.
C.
D.

Answer

C

Explanation

`f=vec(E),vec(ds)`
since `r lt lt R` so we can consider electric field is constant throughout the surface of smaller ring.
hence `f=E prop(x)/((R^(2)+x^(2))^(3//2))`