The field normal to the plane of a wire of `n` turns and radis `r` which carriers `i` is measured on the axis of the coil at a small distance `h` from the centre of the coil. This is smaller than the field at the centre by the fraction.

Options

A. `(3)/(2)(a^(2))/(r^(2))`
B. `(2)/(3) (a^(2))/(r^(2))`
C. `(3)/(2) (a)/(r)`
D. `sqrt((3)/(2)) (a^(2))/(r^(2))`

Answer

A