The distribution of magnetic field due to a current carrying circular loop is as follows:

A circular loop can be considered to be made up of a large number of very small straight wires. A magnetic field is produced by an electric current flowing through every such wire add up in case of a circular loop. The magnetic field lines form closed loops around the current carrying loop. At the center of circular wire, field lines become straight and perpendicular to the plane of coil. Right hand thumb rule can be used to determine the direction of magnetic field produced due to a current carrying circular wire. The thumb gives the direction of magnetic field if the fingers are curled in the direction of current flow.

The magnetic field at any arbitrary point is the addition of the field produced by each turn in a coil containing n turns. Thus, if a current carrying coil has n turns, the field produced at any point is n times as large as that produced by a single turn.

OR

When a conductor is made to move inside a magnetic field or a magnetic field is made to change around a conductor, electric current is induced in the conductor. In other words, when a conductor is brought in relative motion with a magnetic field, a potential difference is induced across it. This phenomenon is known as electromagnetic induction.

An experiment to show that a current is set up in a closed loop when external magnetic field passing through the loop increases or decreases is as follows:

For this experiment, a magnet, a coil and a galvanometer are need. The coil is connect to the galvanometer to measure the current through the coil.

As shown in the diagram, the magnet is made to move towards or away from the closed loop. The changes in current is noted from the galvanometer.

When the magnet is brought towards the loop, magnetic field through the loop increases. It is observed that the current in the circuit increases as well due to electromagnetic induction. In a same way, when the magnet is made to move away from the loop, the current in the circuit decreases.