Question

A long straight wire in the horizontal plane carries a current of 50 A in north to south direction. Give the magnitude and direction of B at a point 2.5 m east of the wire.

Answer 1

I = 50 A, r = 2.5 m
B = \(\frac{\mu_{0} I}{2 \pi r}\)
= \(\frac{4 \pi \times 10^{-7} \times 50}{2 \pi \times 2.5}\)
= 4 x 10^-6 T upwards. (due to the wire alone)