A horizontal overhead powerline is at a height of 4m from the ground and carries a current of 100 A from east to west. The magnetic field directly below it on the ground is ($μ_0 = 4π × 10^{-7}\, TmА^{-1}$)

$5 × 10^{-6} T$, southward

$ B = \frac{\mu_0 I}{2\pi r} = \frac{4\pi \times 10^{-7}\times 100}{2\pi \times 4} = 5 \times 10^{-6} T \text { Southward}$