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

Answer

C

Explanation

Magnetic field due to a circular coil having n turns at a distance x on its axis is give by
`B=(mu_(0))/(4pi)*(2pi n ir^(2))/((x^(2)+r^(2))^(3//2))`
`:. B prop=(nr^(2))/((x^(2)+r^(2))^(3//2))`