Problem 1: At what distance from a long straight wire carrying a current of 10 A is the magnetic field equal to the earth’s magnetic field of 5 * 10-5 T.
Given data I = 10 A B = 5 * 10-5 T
Required r =?
When current passes through a conducting wire, a magnetic field is produced around the wire. The value of the magnetic field at any point distant r from the wire is given by Ampere’s Circuital Law.
Where μ0 is called the permeability of free space and its value is 4π * 10-7 wb/A.m.
The value of r (distance from the wire) can be calculated from the above equation.
Put the values in the above equation from the given data