Magnetism and Electromagnetism - SS1 Physics Past Questions and Answers - page 3

Electromagnetic induction is the process of producing an electric current in a conductor by changing the magnetic field around it. When a conductor, such as a wire, is exposed to a changing magnetic field, an electromotive force (emf) is induced in the conductor, which causes an electric current to flow. This phenomenon was first discovered by Michael Faraday.

The basic principle behind electromagnetic induction is Faraday's law, which states that the magnitude of the induced emf is directly proportional to the rate of change of the magnetic field. This induced current can be utilised to generate electricity in devices like generators, where a rotating magnet or electromagnet is used to create a changing magnetic field relative to the conductor.

Lenz's law is a fundamental principle in electromagnetic induction formulated by Heinrich Lenz. According to Lenz's law, the direction of the induced current in a conductor is such that it opposes the change that caused it. In other words, when a changing magnetic field induces an emf in a conductor, the resulting current creates a magnetic field that opposes the original change in the magnetic field. 

This law is based on the principle of conservation of energy. By opposing the change, Lenz's law ensures that the work done by the induced current to create the opposing magnetic field is in accordance with the principle of energy conservation. Lenz's law plays a crucial role in understanding the behaviour of induced currents and helps explain phenomena such as the generation of back emf in electric motors and the self-induction in coils.