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  Statically induced e.m.f and Dynamically induced e.m.f   Lenz’s Law of Electromagnetic induction  Fleming’s Right hand Rule   Faraday’s Laws of Electromagnetic Induction  What is Rogowski coil ?


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Faraday’s Laws of Electromagnetic Induction

Whenever electric current flows through a conductor, a magnetic field will set up in the space surrounding the conductor. So, we can say that when the electron is in motion, they produce a magnetic field. Alternatively, when a magnetic field cuts a conductor, it produces a flow of electrons in the conductor. The scientist, Mr. Michael Faradays, had invented the electricity by “converting magnetism” and he had formulated the basic laws of electromagnetic induction, upon his law is based the operation of motors, generator, and transformer etc.

Now we describe how does “induced e.m.f” produce in a conductor?

Let, a stationary bar magnet is placed close to a insulated coil whose terminals are connected a sensitive Galvanometer (G) which is shown in figure. When the both magnet & coil are stationary, there will be no deflection in the galvanometer.
Now, the magnet is suddenly brought closer to the coil in position CD from the position AB , (which is shown in fig. ). Then a momentary deflection has been observed in galvanometer and that deflection stays as long as the magnet is in motion relative to the coil. When the magnet becomes again stationary at its new position CD, the deflection of galvanometer reduces to Zero.
Next, If the magnet is suddenly with drawn away from the coil that means sifted from the position CD to AB. Similarly, a momentary deflection has occurred in galvanometer and it persists so long as the magnet is in motion, but the deflection is in a direction opposite of the previous defection. From the deflection of the galvanometer, it can be indicated that some e.m.f is produced in the coil and this induced e.m.f exists so long as the change of flux exists. And Stationary flux will never induce any e.m.f in the stationary conductor.

We can get the same result, when the bar magnet is stationary and conductor is suddenly away or towards the magnet. If a conductor AB laying within a magnetic field and a galvanometer is connected with that conductor which is shown in fig.
It is found that whenever the conductor is moved up or down, a momentary deflection is produced in the galvanometer. It means that some e.m.f is induced in the conductor and the magnitude of e.m.f depends on the quickness of movement of conductor AB. It has been also observed that when the conductor AB is moved parallel to the direction of flux, so that it does not cut the flux. There will be no deflection in the galvanometer, that means there is no induced e.m.f in the coil.

From the above experiment, It has been concluded that whenever a conductor cuts or shears the magnetic flux, an e.m.f is always induced in the conductor and amount of e.m.f fully depends on the rate of cuts magnetic flux by the conductor , but not depends on the strength of magnetic flux.

Now we discuss Faraday’s laws of Electromagnetic induction below

Faraday’s Laws of Electromagnetic Induction:-

1) First Law: - Whenever a conductor cuts magnetic flux , an e.m.f is induced in that conductor.

2) Second Law:- The magnitude of the induced e.m.f is equal to the rate of change of flux linkages.


Now, we describe the explanation of induced e.m.f in a coil.
Let, N= No. of turns of a coil,
Φ1= Initial value of magnetic flux which cuts the coil,
Φ 2= Final value of flux in time t seconds.
flux-linkages is meant the product of number of turns by flux linked with the coil,
So, The initial flux linkages = N φ1
And final flux linkages = N φ2,

According to Faradays law of electromagnetic induction, the induced e.m.f is the rate of change of flux linkage.

Therefore, The induced e.m.f (e)=(NΦ2-NΦ1)/t Wb/ Sec, or Volt
Or, e= N (Φ21)/t Volt,
In the differential from, we get ,
e = d/dt(NΦ) Volt
e = NdΦ/dt volt

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