Question

A surveyor is using a magnetic compass 5.6 m below a power line in which there is a steady current of 140 A. (a) What is the magnetic field in microteslas at the site of the compass due to the power line? (b) Will this field interfere seriously with the compass reading? The horizontal component of Earth’s magnetic field at the site is 20 µT.

Answer 1

Answer:

(a) B = 5.6 micro Tesla

Explanation:

Current in the wire, i = 140 A

distance, r = 5 m

The formula for the magnetic field at a distance r due to the current carrying wire

$B=\frac{\mu _{0}}{4\pi }\times \frac{2i}{r}$

$B=10^{-7}\times \frac{2\times140}{5}$

B = 5.6 x 10^-6 Tesla

B = 5.6 micro Tesla

(b) As the magnetic field of earth at this site is 20 micro tesla so the magnetic field due to current carrying wire interfere the magnetic compass.