A circular coil A has a radius R and current flowing through it is I. Another circular coil B has a radius 2R and if 2I is the current flowing throgh it, then the magneitc field at the centre of the circular coil are in the ratio (i.e, `B_A` to `B_B`) of

Options

A. `4:1`
B. `2:1`
C. `3:1`
D. `1:1`

Answer

A

Explanation

`B_A = (mu_0 I)/(2R) and B_B = (mu_0 (2I))/(2(2R)) = (mu_0 I)/(2R) implies B_A : B_B = 1 : 1`