Electrical Engineering ⇒ Topic : Faradays Laws

Faraday's Laws

Faraday's first law of electromagnetic induction states that an emf is induced in a coil when the magnetic flux linking the coil changes with time.

Faraday's second law states that this included voltage is proportional to the time rate of change of the current which produced the magnetic field, or the magnitude of the induced emf is proportional to the time rate of change of flux linkages. It is expressed as

where e denotes the emf induced in the coil or circuit

ψ - flux linkages = Nφ

N - no. of turns

φ - flux in Weber's

The minus sign takes into account the sense of the induced emf dictated by Lenz's law.

An induced emf can be either (i) dynamically induced, or (ii) statically induced. In the former case, the field is stationary and conductors are moving this arrangement is used in dc generators and motors. In the second case, the conductor or coil is stationary and the flux linking with it changes. This arrangement is used in transformers and alternators

Faraday's Laws

First law

It states that

whenever there is variation of magnetic flux linked with a coil, an e.m.f is induced in it.

                                                                  OR

the e.m.f is induced in a conductor whenever the coil cuts the magnetic flux.

Second law

It states that

the magnitude of this induced e.m.f is the rate of change of flux linkage.

Suppose that the initial flux be Φ₁ and final flux be Φ₂ in time t. Let the turns of the coil be N.Therefore, initial flux linkage is NΦ₁ and final flux linkage is NΦ₂.

In differential form, we can put the above equation as

                                                                                                     .................   (1)

Faraday's Laws of Electrolysis :-

First law :-It states that the mass of ion liblerated at an electrode is directly proportional to the quantity of electricity, i.e., charge

which passes through the electrolyte If m = mass of ions liberated Q = quantity of electricity = I x t where jis tle current and t is the time

Z = Constant, known as electrochemical equivalent (I.C.E.) of the substance then m = ZIt

Second law:- It states that the masses of ions of different substances liberated by the same quantity of electricity are proportional to their

chemical equivalent weights Electroplating is the application of the principles of electrolysis.