The magnetic induction at a point, distance x from the centre, on the axis of a circular current carrying coil is inversely proportional to (if `xgtgt` Radius of coil)

Options

A. X
B. `X^(2)`
C. `X^(-3)`
D. `X^3/2`

Answer

C

Explanation

Magnetic induction at a point, distance x from the centre, on the axis of a circular current carrying coil is
`B=(mu_(0)nia^(2))/((a^(2)+x^(2))^(3/2))`
`xgtgta`. So a can be neglected
`B=(mu_(0)nia^(2))/(x^(3))`
`B prop (1)/(x^(3))`
`B prop (1)/(x^(-3))`