Question

A bar magnet is held with its length along the axis of a closed coil. Initially, the south pole of the magnet faces the coil. If the magnet is moved towards the coil, explain how a current is induced in the coil and in what direction.

Hint:

\textbf{Lenz's Law} states that the direction of the induced current will always oppose the change in magnetic flux. This ensures that energy is conserved during electromagnetic induction.

Answer 1

When a bar magnet is moved towards a coil, the magnetic flux through the coil changes, leading to the induction of a current. This phenomenon is explained by Faraday's Law of Induction, which states that a change in magnetic flux through a coil induces an electromotive force (emf) in the coil. Induced Current: 1. Direction of the Induced Current: - According to Lenz's Law, the direction of the induced current will oppose the change in magnetic flux. - Since the south pole of the magnet is facing the coil and the magnet is being moved towards the coil, the magnetic flux through the coil is increasing in the direction of the south pole of the magnet. - The coil will induce a current that creates a magnetic field opposing the increasing magnetic flux. To do this, the coil will behave as if it has a north pole facing the approaching south pole of the magnet. 2. Nature of the Induced Current: - When the south pole of the magnet is brought closer to the coil, the coil generates a current that creates a magnetic field which opposes the south pole of the magnet. - Therefore, the induced current will flow in such a direction that it opposes the magnet's south pole, which can be determined by using the right-hand rule for coils. 3. Right-Hand Rule: - According to the right-hand rule for solenoids, the direction of the current is such that if you curl the fingers of your right hand in the direction of the current, your thumb will point in the direction of the magnetic field inside the coil. - In this case, since the south pole of the magnet is approaching, the coil will generate a north pole on the side facing the magnet to oppose the motion of the south pole. Thus, a current is induced in the coil, and its direction is such that the magnetic field created by the coil opposes the increase in magnetic flux due to the approaching south pole of the magnet. Final Answer: The induced current in the coil will flow in a direction that creates a magnetic field opposing the approaching south pole of the magnet.