A bar magnet is close to a metal loop. When this magnet is...

A bar magnet is close to a metal loop. When this magnet is suddenly moved to the left away from the loop, as shown in Figure $21.55,$ a counterclockwise current is induced in the coil, as viewed by an observer looking through the coil toward the magnet. Identify the north and south poles of the magnet.

Key Concepts

Electromagnetic Induction

This concept describes how a changing magnetic flux through a conductor, like a loop, produces an induced electromotive force (emf) or current. When the magnetic environment of the loop changes – for example, when a magnet is moved – an electric current is generated in the loop as dictated by Faraday’s law.

Lenz's Law

This law states that the direction of the induced current is such that its magnetic field opposes the change in the original magnetic flux that produced it. In the context of the magnet moving away from the loop, Lenz’s law helps determine the direction of the induced current by ensuring that the magnetic field created by the induced current tries to maintain the lost magnetic flux.

Right-Hand Rule for Coils

This rule provides a method to determine the direction of the magnetic field produced by a current-carrying conductor in the shape of a loop. For a coil, if you curl the fingers of your right hand in the direction of the current, your thumb points in the direction of the induced magnetic field inside the coil. This rule is essential for linking the observed direction of the induced current to the polarity of the magnetic field that the coil creates.

Magnetic Field of a Bar Magnet

A bar magnet has a magnetic field that emerges from its north pole and enters its south pole. Understanding this concept is vital when determining which face of a magnet is near a loop causing induction. If the magnetic field passing through the loop is directed outward (away from the magnet, based on the induced current's effect), then the face of the magnet near the loop must be the north pole.

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