Magnetic field due to a ring having n turns at a distance `x` on its axis is proportional to (if `r =` radius of ring)

Options

A. `r/((x^2+r^2))`
B. `(nr^2)/((x^2+r^2)^(3//2))`
C. `(r^2)/((x^2+r^2)^(3//2))`
D. `(n^2 r^2)/((x^2+r^2)^(3//2))`

Answer

B