Physics – 4.5.1 Electromagnetic induction | e-Consult

Setup: A simple setup involves a coil of wire and a magnet. The magnet is moved either towards or away from the coil, or vice versa. The diagram below shows a common arrangement.

Principles Involved:

• Changing Magnetic Flux: When the magnet moves, the magnetic flux linking the coil changes. Magnetic flux (Φ) is a measure of the amount of magnetic field passing through a given area. It is calculated as Φ = B x A x cos θ, where B is the magnetic field strength, A is the area, and θ is the angle between the magnetic field and the area.
• Faraday's Law of Induction: Faraday's Law states that a changing magnetic flux through a circuit induces an e.m.f. in the circuit. The magnitude of the induced e.m.f. is proportional to the rate of change of the magnetic flux. The negative sign indicates the direction of the induced e.m.f. (Lenz's Law).
• Lenz's Law: The induced e.m.f. will cause a current to flow in a direction that opposes the change in magnetic flux that produced it. This is known as Lenz's Law. For example, if the magnet is moving towards the coil, the induced current will create a magnetic field that opposes the motion of the magnet.

In summary: Moving a magnet near a coil of wire changes the magnetic flux through the coil, inducing an e.m.f. in the coil. This e.m.f. drives a current in the coil.