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Faraday's Law of electromagnetic induction | Lenz's law | Law of electromagnetic induction

Faradays Law of  Electromagnetic Induction :

Faraday's laws state that an emf is induced in a circuit which is

(i) Directly proportional to the time rate of change of flux enclosed by the circuit.

(ii) Directly proportional to N the no. of turns of the circuit.

Combining, the two laws, Faraday's laws of induction can be expressed mathematically as



Here negative sign is due to Emil Lenz, who after Faraday's experiments suggested

that the direction of the induced current is always such as to oppose the action that produced it.

As we know Faraday's law as given by equation (ii.1) is one of the two basic relationships

upon which the whole theory of electromagnetic and electromechanical energy conversion devices are based and today we have the generator and motor (electric) operating based on this theory.


Also, Faraday was the first to identify emf of self-induction, i.e., here we have only one coil

and it is connected to a de source through a switch. When current is flowing through this coil

and the circuit is interrupted through the switch an emf is induced in the coil. This is known as

emf of self-induction expressed mathematically 



Where L is a proportionality constant called

The- efficiency of self-inductance depends upon the medium and other physical parameters we will discuss in a later section of this chapter. 


LENZ's LAW :


As in-laws of mechanics, to every action, there is an equal and opposite reaction. The fact that

this law holds good in electromagnetism was discovered by Emil Lenz.


Lenz law states that this induced current always develops a flux that opposes the very

cause it is due to. This law refers to induced currents and therefore, implies that it applies

to closed circuits only. However, if the circuit is open it is possible to find the direction of induced emf by assuming as if the circuit were closed. 
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