Question

A circular coil of radius `R` carries a current `i`. The magnetic field at its centre is `B`. The distance from the centre on the axis of the coil where the magnetic field will be `B//8` is
A. `sqrt(2)R`
B. `sqrt(3)R`
C. `2R`
D. `3R`

Answer 1

Correct Answer - 2
`B=(mu_(0)nir^(2))/(2(r^(2)+x^(2))^(3//2))=(1)/(8)xx(mu_(0)ni)/(2r)`