Physics – 4.1 Simple phenomena of magnetism | e-Consult

When a bar magnet is moved towards a coil of wire, the magnetic flux through the coil changes. Magnetic flux (Φ) is a measure of the amount of magnetic field lines passing through a given area. As the magnet approaches, more magnetic field lines pass through the coil, increasing the magnetic flux.

Faraday's Law of Induction states that a changing magnetic flux through a coil induces an electromotive force (EMF), which drives a current. The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux. Mathematically, this is expressed as: EMF = -N (dΦ/dt), where N is the number of turns in the coil and dΦ/dt is the rate of change of magnetic flux.

The magnitude of the induced current is proportional to the magnitude of the induced EMF. Therefore, a faster speed of the magnet results in a greater rate of change of magnetic flux, leading to a larger induced EMF and a larger induced current. Similarly, increasing the number of turns in the coil (N) increases the total magnetic flux per turn, resulting in a larger induced EMF and a larger induced current. The negative sign in Faraday's Law indicates Lenz's Law, which states that the induced current creates a magnetic field that opposes the change in the original magnetic flux.