Electromotive force is defined as the electrical action produced by a non - electrical source. Devices provide emf by converting other forms of energy into electrical energy. Examples of such devices are batteries and generators. Electromotive force or emf is the amount of energy per unit electric charge which is imparted by energy source.
EMF or electromotive force is said to be induced when the flux linking with a conductor or coil changes. This change in flux can be obtained in two different ways, either by statically or by dynamically induced emf.
Faraday's law of electromagnetic induction says that the EMF induced in a coil e = - (rate of change of magnetic flux linkage).
The factors affecting induced emf in a coil are:
Number of turns N - The induced emf is directly proportional to the number of turns in the coil.
Area of cross section S - The induced emf is directly proportional to the area of cross section of the coil.
Magnetic field B – The induced emf is directly proportional to the strength of the magnetic field in which coil is rotating.
Angular velocity ω - The induced emf is directly proportional to the angular velocity of the rotating coil.
The induced emf also varies with time and depends on the instant t.
Consider a conducting coil of N turns and area S rotating with a uniform angular velocity \(\vec\omega\) about an axis in the plane of the coil, and perpendicular to a uniform magnetic field of induction \(\vec B.\)
The frequency of rotation of the coil is,
f = ω/2π
Magnetic flux through the loop in the given position is given by:
Therefore, the e.m.f induced in coil rotating in uniform magnetic field is given by ε = −NBSω cos(θo + ωt).
