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: When the current flows through a conductor, it generates a magnetic field around it. This magnetic field lies in a plane that is perpendicular to it. The magnetic field lines form a closed loop, the direction of this field is given by the right-hand thumb rule.

Complete Step by step solution:
According to the question, the direction of current is from east to west.
The magnetic field lines form loops around the length of the circle, in a plane that is perpendicular to its length. The direction of the magnetic field lines can be determined by the right-hand thumb rule.
According to the right-hand thumb rule, if you point the thumb of your right hand towards the direction of the flow of current, and then curl your fingers around it, the direction of the fingers tells the direction of the magnetic field generated around the conductor.
If the current flows in the wire from east to west, the magnetic field line moves a plane that is perpendicular to the wire. That means they travel in the directions, up-down and north-south.
If the right-hand thumb rule is applied to this wire, we find out that the direction of the fingers points in the following order,
North -> down -> south -> Up
To determine the direction of the magnetic field relative to a point that is situated above the wire, we open the fingers (uncurl it) and then keep the tips of the fingers in the “up” direction while still maintaining the direction of the thumb towards the west. Then, the direction of the face of the palm shows the direction of the magnetic field as observed from a point situated above the wire.
The face of the palm points in the north direction. Thus option (C) is the correct option.

Note:
The right-hand thumb rule can be applied for quantities that involve the “curl” operator in mathematics. It involves multiplication of two vector quantities, such that their product rotates along a plane which is perpendicular to one of the vectors.