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

1

Explanation

`B=B_(1)-B_(2)=(mu_(0)i)/(2r_(1))-(mu_(0)i)/(2r_(2)),B=(mu_(0)ni)/(2r)`