Figure shows a coil of radius `2 cm` concentric with a coil of radius `7cm` Each coil has 1000 turns with a current of `5A` . In larger coil, then the current needed in the smaller coil to give the total magnetic field at the centre equal to `2mT` is

Options

A. 1.49A
B. 1.84A
C. 2.88A
D. 3.4A

Answer

A

Explanation

`B = B_1 - B_2 = (mu_0i)/(2r_1) - (mu_0 i)/(2r_2) , B = (mu_0 "ni")/(2r)`