Question

A surveyor is using a magnetic compass 6.4 m below a power line in which there is a steady current of 120 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:

Explanation:

Magnetic field due to a long current carrying conductor

μ₀ / 4π x 2i / r  ( i = current , r = distance of point from wire )

= 10⁻⁷ x 2 x 120 / 6.4  ( i = 120 A , r = 6.4m )

= 37.5 x 10⁻⁷ T .

= 3. 75 X 10⁻⁶ T .

= 3.75 µT.

b )

The direction of this field will be horizontal hence it will affect magnetic needle.

Answer 2

Answer:

Explanation:

distance between compass and the wire, r = 6.4 m

current in the wire, i = 120 A

(a)

The magnetic field due to the current carrying conductor is

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

$B = 10^{-7}\times \frac{2\times 120}{6.4}$

B = 3.75 x 10^-6 Tesla

(b)

The magnetic field due to the earth is

B' = 20 micro Tesla = 20 x 10^-6 tesla

Yes, the magnetic filed due to current carrying wire interfere the magnetic compass.