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 above the line?

Question

Accepted Answer

(1) 1.2 × 10⁻⁵ T, towards north. Given: a long straight horizontal wire carrying I=90 A from east to west; the point lies r=1.5 m above it. Idea: for a long straight wire B=(μ₀I)/(2π r), and the direction follows the right-hand rule — thumb along the current, fingers curling the way ⃗B points. B=(4π×10⁻⁷×90)/(2π×1.5)=(2×10⁻⁷×90)/(1.5). =1.2×10⁻⁵ T. Direction: with the thumb pointing west, the curled fingers run from south to north over the top of the wire, so at a point above the line ⃗B is towards the north.

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 above the line?

Step-by-step solution

Why the other options are wrong