The magnetic field due to a current flowing through an infinitely long wire is given by `B = (mu*I)/(2*pi*r)` where B is the magnetic field, mu is the permeability of free space and equal to `4*pi*10^-7` T*m/A, and r is the radial distance.

The Earth's magnetic field is approximately `5*10^-5` T. If a wire carries a current of 5 A, the magnitude of the magnetic field due to the current is `5*10^-5` T at a distance r where:

`5*10^-5 = (4*pi*10^-7*5)/(2*pi*r)`

=> r = `(4*pi*10^-7*5)/(2*pi*5*10^-5)`

=> r = `(2*10^-2)`

**The magnetic field around the wire is `5*10^-5` T at a distance `2*10^-2` m from the wire.**

**Further Reading**

## We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

- 30,000+ book summaries
- 20% study tools discount
- Ad-free content
- PDF downloads
- 300,000+ answers
- 5-star customer support

Already a member? Log in here.

Are you a teacher? Sign up now