Electromagnetic Induction of Class 12
To explain the above results Faraday introduced the concept of magnetic flux ΦB, which is defined as
ΦB = = B A cos θ(uniform B)
and ΦB = (non-uniform B)
The SI unit of magnetic flux is the weber (Wb)
1 Wb = (1 T) ( 1m2)
The generation of an electric current in a circuit implies the existence of an emf. Faraday stated,
The induced emf along any closed path is proportional to the change of magnetic flux rate through the area bounded by the path.
E ∝ (4.1)
The three terms represent the contributions from the rate of change of B, A, and θ, respectively to the rate of change of flux. In a given situation, more than one of these may contribute.
The negative sign in the last term signifies that an increase in θ leads to a decrease in flux.
Note that the induced emf is not confined to a particular point. It is distributed around the loop.