Question

A current-carrying power line carries current from west to east. The direction of the magnetic field $1m$above is:

• A. North to south
• B. South to north
• C. East to west
• D. West to east

Answer 1

The correct option is A

North to south

Explanation for the correct option

A: North to south

1. According to the basic crux of the “right-hand thumb rule” if the right thumb points in the direction of the electric current, then the direction of curling of the fingers gives the direction of the magnetic field as depicted in the figure shown above.
2. In the given problem, the current is flowing from the “west to east” direction and if we point the right thumb in the direction of the current i.e in the “east” direction, our fingers will curl in the “north-south” direction which gives the direction of the magnetic field.
3. The diagram below clearly indicated that the magnetic field at point “B” above the current-carrying wire will be in the north-south direction.

Hence, option (A) is correct.