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^(2)/((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

Here r = radius of ring
I = current
n = number of turns
The magnetic field at x distance from the centre of ring
`B=mu_(0)/(4pi)(nIr^(2))/((x^(2)+r^(2))^(3/2))rArrBprop(nr^(2))/((x^(2)+r^(2))^(3/2))`