Question

How much current must flow through a long straight wire for the magnetic field strength to be 1.0 mT at 1.0 cm from a wire? (?0 = 4?

Answer 1

B=1.0 mT=1.0*10-3 T

l= 1.0 cm =0.01 m

$\mu _{0}=4\pi *10^{-7}$

Lets I= current flow

$B=\frac{\mu _{0}I}{2\pi l}$

$I=\frac{B*2\pi *l}{\mu _{0}}$

$I=\frac{1.0*10^{-3}*2\pi *1.0*10^{-2}m}{4\pi *10^{-7}}$

$I=50A$

Answer is 50A

Answer 2

B=mu*I/2*3.14*R

1*10^-3=4*3.14*10^-7*I/2*3.14*1*10^-2

I=0.5*10^-3/10^-5

=50A