Question

A current flows in a conductor from east to west. The direction of the magnetic field at a point above the conductor is:
A. towards east
B. towards west
C. towards north
D. towards south

Answer 1

Hint: This question can be solved using the right hand thumb rule, as this is all about the directions of the flow of current and the magnetic field. Here, we will make use of Maxwell’s right hand thumb rule, as it particularly, represents the direction of the flow of current and the magnetic field.

Complete answer:
The right hand thumb rule represents the orientation of the axis in 3D. But, in our case, we are given with the data as follows. A current flows in a conductor from east to west. Thus, the direction of the magnetic field will neither be the east nor west direction. Therefore, we will make use of Maxwell’s right hand thumb rule.

Maxwell’s right hand thumb rule states that, when the current flows from east to west direction, the magnetic field will move in a clockwise direction, that is, from the direction north to south. Similarly, when the current flows from west to east direction, the magnetic field will move in an anti-clockwise direction, that is, from the direction south to north.
As the direction of the magnetic field at a point above the conductor will be towards the east, for the current flow in a conductor from east to west.

Thus, the option (C) towards north is correct.

Note:
The right hand thumb rule is used to find the cross product, such that, the two of the fingers, that is, the index finger and the middle finger represents the vectors and the third finger, that is, the thumb represents the cross product of the two vectors.