Question

What current (in ampere) must flow in a circular coil of 20 loops of radius 40 cm to produce a

magnetic field of 2

3 10 T 

  at its center?

Answer 1

We use the BIOT SAVART's law for finding the magnetic field B at the center of circular coil.

R= 0.40 m
N = loops = 20
Given B = 2.3 × 10^-7 T. The exponents are not printed properly. ...Assuming. ..

B = μ0 N I/ (2 R)
I = 2 B R /(μ0 N)
I = 2*2.3×10^-7 * 0.40 / (4*pi*10^-7*20) A
I = 7.3 mA.