Question

A horizontal overhead powerline at a height of $5\, m$ from the ground and carries a current of $150\, A$ from East to West. The magnetic field directly below it on ground is

• A. $6 \times 10^{-6} T$ towards South
• B. $6 \times 10^{-6} T$ towards West
• C. $7 \times 10^{-6} T$ towards East
• D. $8 \times 10^{-7} T$ towards North

Answer 1

Answer: (A)

Magnetic field below the wire on the ground is given as

$B =\frac{\mu_{0}}{2 \pi} \cdot \frac{I}{r}$
$=2 \times 10^{-7} \times \frac{150}{5}$
$\left[\because \mu_{0}=4 \pi \times 10^{-7} TmA ^{-1}\right]$
$=6 \times 10^{-6} T$ (toward South)