Question

A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire?

Answer 1

Current in the wire, I = 35 A
Distance of a point from the wire, r = 20 cm = 0.2 m
Magnitude of the magnetic field at this point is given as:

Where,
 μ₀= Permeability of free space
= 4π × 10^–7 T m A^–1

Hence, the magnitude of the magnetic field at a point 20 cm from the wire is 3.5 × 10^–5 T.