Why are magnetic field lines in a circular wire straight at the centre?
Solution:
The direction of the magnetic field of every small section of the circular loop can be found by using the right-hand thumb rule. As per the rule, If you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of the current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field. That means when the electric current is in the upward direction around the axis of the circular conductor, the magnetic field lines are in an anti-clockwise direction while with the downward flow of electric current, the magnetic field lines are in a clockwise direction.
At the centre the cumulative effect of all the field lines due to each small section is a straight line. The direction of the magnetic field at the centre of the circular coil is perpendicular to the plane of the coil i.e. along the axis of the coil.
The direction of the magnetic field of every small section of the circular loop can be found by using the right-hand thumb rule. As per the rule, If you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of the current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field. That means when the electric current is in the upward direction around the axis of the circular conductor, the magnetic field lines are in an anti-clockwise direction while with the downward flow of electric current, the magnetic field lines are in a clockwise direction.
At the centre the cumulative effect of all the field lines due to each small section is a straight line. The direction of the magnetic field at the centre of the circular coil is perpendicular to the plane of the coil i.e. along the axis of the coil.