Question

A current carrying power line carries current from west to east. The direction of magnetic field $1\text{ m}$ above is:
A. North to south
B. South to north
C. East to west
D. West to east

Answer 1

The direction of magnetic field can be found out by the right-hand rule. According to the right-hand rule we need to consider the thumb of the right hand and see whether the current flows in its direction or not. If the current flows in the direction of the thumb then by curling the fingers of the same hand we can find out the direction of the magnetic field.

Complete step by step answer:
To find out the direction of the magnetic field, first let us consider our right hand and then place our right hand in such a way that the thumb points in the east direction, i.e., in the direction of the flow of current. We can observe that our fingers are now pointing in the north direction and the normal vector of the palm is normal to the plane of paper. Now, we will curl our fingers and we can observe that the fingers are curling from north to south direction which means that the direction of magnetic field $1\text{ m}$ above the current carrying power line is north to south.
So, the correct answer is “Option A”.

Note: If we wish to find out the direction of the magnetic field at some distance that is located below the wire then the direction would have been different. Also, if the direction of the current flowing the wire is changed, then even the direction of magnetic would have changed. So, we have to be careful while using Maxwell's right hand thumb rule.