Q.

The ratio of magnetic field at the centre of a current carrying coil of radius r to the magnetic field at distance r from the centre of the coil on its axis is x:1. The value of x is _______.                   [2023]


Ans.

(8)

Magnetic field at centre (B1)=μ0I2r

Magnetic field on axis =μ0Ir22(r2+d2)3/2

Value of d=r (given)

B2=μ0I42r

B1B2=μ0I2r×42rμ0I=221=81

x=8