Question

A current through a horizontal power line flows in the east to west direction. What is the direction of magnetic field at a point directly below it and at a point directly above it?

Answer 1

The current is in the east-west direction. Applying the right-hand thumb rule, we get that the direction of magnetic field at a point below the wire is from north to south. The direction of magnetic field at a point directly above the wire is from south to north.