In this IIT JEE physics video lecture, we are going to talk about electromagnetic induction. In this physics video the topics covered are;

• Magnetic flux
• Gauss’s law for magnetism
• EMI
• And some exemplary problems

So let’s begin with magnetic flux. The direction of magnetic flux is same as the magnetic field lines. If they are close, then they are dense. Magnetic field or magnetic flux is always in a closed loop, which means it does not start at a particular point and ends at a particular point. Magnetic flux is a number of magnetic field lines. It is measured by ɸ and it is,

ɸ= EACosθ, its unit is tesla/m2 or Weber/m2

Flux is linked with the area. After that, we have discussed an exemplary problem. Moving on, we have talked about Gauss’s law for magnetism, a pretty simple law.  If suppose we need to find the linked flux from an irregular surface and take one small surface as dA. Let B be the magnetic field. Then the flux is,

ɸ = Flux;

The total flux in the case of a closed surface irrespective of absence or presence of magnet inside it. The total flux will be,

ɸ =  0

This is Gauss’s law of magnetism; therefore the net flux is always zero. Further, we have discussed EMI. EMI stands for Electronic Magnetic Induction. Because of the magnetic field, an electric field is generated. The time-varying magnetic field induces an electric field and time varying electric field induces a magnetic field in the space. If suppose there is a proton at rest, and you are moving towards the proton. You will now experience a change in magnetic field in your frame of reference.  If now we move the magnet, then a magnetic field will be generated.

Further, we have discussed flux linked. If suppose we have spherical coil and B is perpendicularly passing through it and A is the area of cross-section, then flux is 1. Now if the coil has ‘N’ is the number of turns in the coil, the linked flux is,

ɸ = Nɸ = NBACosθ

We can calculate it for a solenoid also. Further, we have Faraday’s experiment. In the above video, there is demonstrating video which will help you get a better understanding. The statement of Faraday’s first law is, “When the flux linked with a coil or circuit keeps changing an e.m.f.  is developed in the circuit or the coil.” If the circuit is closed then the current will flow.