Question

A horizontal overhead power line carries a current of 90 A in east to west direction. What is the magnitude and direction of the magnetic field due to the current 1.5 m below the line?

Answer 1

Current in the power line, I = 90 A

Point is located below the power line at distance, r = 1.5 m

Hence, magnetic field at that point is given by the relation,

B = `(mu_0 2"I")/(4pi"r")`

Where,

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

B = `(4pi xx 10^-7 xx 2 xx 90)/(4pi xx 1.5)`

= 1.2 × 10^–5 T

The current is flowing from East to West. The point is below the power line. Hence, according to Maxwell’s right-hand thumb rule, the direction of the magnetic field is towards the South.