The figure below shows a current-carrying loop passing through a sheet of cardboard. Draw three magnetic field lines on the cardboard.
Give two factors on which the magnitude of the magnetic field at the centre of the loop depends.

(N/A) The magnetic field lines around a current-carrying circular loop are concentric circles near the points where the wire passes through the cardboard. As we move towards the centre of the loop,the circles become larger and larger,and near the centre,the field lines appear as straight lines.
The magnitude of the magnetic field $(B)$ at the centre of a circular current-carrying loop depends on the following two factors:
$(i)$ The strength of the current $(I)$ flowing through the loop: The magnitude of the magnetic field is directly proportional to the current $(B \propto I)$.
$(ii)$ The radius of the loop $(r)$: The magnitude of the magnetic field is inversely proportional to the radius of the loop $(B \propto 1/r)$.