Electric and Magnetic Fields: Electromagnetic Induction

Electromagnetic Induction is the process of generating an electric current by changing the magnetic field in a closed loop of wire.
Faraday’s Law states that the electromotive force (EMF) induced in a circuit is directly proportional to the rate of change of flux linkage.
The equation to represent Faraday’s Law is ε = -dΦ/dt, where ‘ε’ is the induced EMF, and ‘dΦ/dt’ is the rate of change of flux.
The negative sign in Faraday’s Law is due to Lenz’s Law which states that the direction of induced current is such as to oppose the change in magnetic field producing it.
Flux linkage is the product of the number of turns in a coil and the flux through it. It is measured in Weber-turns (Wb-turns).

An electric generator is a device that converts kinetic energy into electrical energy using the principle of electromagnetic induction.
In an A.C. generator, a coil of wire rotates in a magnetic field, inducing an alternating current.
The output voltage from an A.C. generator varies sinusoidally, and it is directly related to the rate at which the coil turns in the magnetic field.
By contrast, in a D.C. generator, direct current is generated through use of split-ring commutators.

A transformer is a device that uses electromagnetic induction to change the voltage of an alternating current.
It consists of two coils of wire, the primary coil and the secondary coil, which are wound around the same soft iron core.
In an ideal transformer, Power_out = Power_in, or VpIp = VsIs, where ‘V’ is voltage, ‘I’ is current, and the subscripts ‘p’ and ‘s’ refer to the primary and secondary coils respectively.

Electromagnetic induction is used in power generation, electric motors, transformers, induction cooking, wireless charging, and metal detectors among many other applications.
Transformers are used in power transmission to step up the voltage (making it higher) for efficient long-distance transmission and to step down the voltage for use in homes and businesses.