Understanding Faraday's Law of Electromagnetic Induction

Faraday's Law of Electromagnetic Induction

Welcome to our blog post on Faraday's Law of Electromagnetic Induction! In this post, we'll dive deep into the fundamentals of electromagnetic induction and explore how Michael Faraday discovered this revolutionary concept. We'll also explore the key principles behind Faraday's Law and how it relates to the production of electrical energy. Whether you're a student of physics or simply interested in the science behind electricity, this post is a must-read. So, let's get started!

Hello friends, welcome back to Physics and Animation blog. In this post, we will discuss Faraday's Law of Electromagnetic Induction and the experiment that led to its discovery.

The phenomenon of electromagnetic induction was independently discovered by Michael Faraday in 1831 and Joseph Henry in 1832. Faraday was the first to publish the results of his experiments. This well-known phenomenon is still charging and moving the world, without which we could not imagine our life. So let's talk about Faraday's experiment of electromagnetic induction.

Faraday's experiment:-

In this experiment, we take a simple coil with a Galvanometer connected in series, and a permanent bar magnet on which an N and S represent the North and South poles of a bar magnet, respectively. When we move the bar magnet towards the coil, an indication of electric current can be seen through the deflection of the needle in the Galvanometer. But when we stop moving the bar magnet, the Galvanometer does not show any indication of electric current. Similarly, when we move the bar magnet away from the coil, the same phenomenon occurs. As we move the bar magnet away from the coil, there is an indication of electric current in the coil, which can be seen by the needle of a Galvanometer. But this time, the needle is deflected in the opposite direction. When we stop moving the bar magnet, there is no indication of an electric current.

Now the question arises, what is happening? What causes the charges to flow in the coil? Is it because of the motion of the magnet? The answer is no. So how is it happening? Let's explore it.

As we all know, a bar magnet consists of magnetic field lines emerging from the North Pole and entering the South Pole of a bar magnet. Therefore, when we move our magnet towards the coil, the magnetic field lines linking to the cross-section of the coil increase, or we can say that the magnetic flux linking to the coil increases. Because of the changing magnetic flux (i.e., the changing number of magnetic field lines passing through the cross-section of the coil), electric current is induced in the coil, this happens only if the circuit is closed. But when we stop moving the bar magnet, there is no indication of electric current in the Galvanometer.

Similarly, when we start moving the bar magnet away from the coil, the magnetic field lines linking to the coil decrease, or the magnetic flux changes. Again, there is an indication of electric current as long as we are moving the bar magnet away from the coil. It's interesting to note that this time also, the induction of electric current stops as the bar magnet stops moving. It is important to understand that the induction of electric current occurs only when the magnetic flux changes, i.e., when there is a change in the number of magnetic field lines passing through the cross-section of the coil.

You might still be confused about how you can believe that induction of electric current is because of changing magnetic flux and not because of the motion of a magnet. To make it clear, let's do another experiment. This time, we will replace the magnet with another coil, which is connected in series with a battery in an open circuit. Now, when we close the circuit, the Galvanometer, which is connected to the edges and coil, shows an indication of the induced current for just that moment. A similar phenomenon occurs when we open the circuit, but this time, we don't have any magnet or motion of a magnet. Then what is the cause of that instantaneous current, which only induces for the moment when the circuit closes or opens?

Let's visualize what happens when we close a circuit. 

As we close the circuit Electric current takes some time to reach its highest value due to the effect of electromagnetism. The magnetic field of a coil changes from zero to its highest value in a way that the magnetic field lines of the coil start linking to the cross-section of the adjacent coil. Does the change of magnetic flux take place in the adjacent coil, which induces the electric current in a coil for an instant until the current achieves its highest value or starts producing a magnetic field? This change in magnetic flux takes place in a very short period of time. So it's clear that electric current is induced in a coil due to the changing magnetic flux and not because of the motion of the magnet, as in this case, there is no motion involved, yet current is still induced in the distant coil, which is connected in series with the galvanometer. A similar thing happens when the circuit is opened, and the indication of electric current can be seen clearly in the galvanometer.

Faraday's First Law of Electromagnetic Induction:-

Michael Faraday first experienced this phenomenon of electromagnetic induction and named it Faraday's First Law of Electromagnetic Induction. 

"It states that whenever there is a change in magnetic flux linking to a conductor, an electromotive force (EMF) is induced in a conductor, and if the circuit is closed, this EMF produces current in the conductor." 

However, Faraday's first law of electromagnetic induction only talks about the induced EMF and current, but it does not explain what decides the magnitude of EMF and induced current in the conductor or a coil. Therefore, to answer this question, Faraday gave the second law of electromagnetic induction.

Farday's Second Law of electromagnetic induction:-

The change of magnetic flux induces current in the conductor, 

"but the magnitude of induced EMF and electric current depends on how fast the magnetic flux, i.e., the number of magnetic field lines passing through the cross-section of the coil, increases or decreases." 

If we repeat the first experiment, but this time move the magnet more rapidly, a higher magnitude of EMF and current will be induced in the coil, which can be seen by the needle of a galvanometer.

Let's try to understand it with the help of a mathematical expression. The magnitude of instantaneous EMF induced is equal to the change of magnetic flux divided by the change in time, i.e., 

EMF = -N(dΦ/dt)

We can say that the magnitude of induced EMF is directly proportional to the rate of change in magnetic flux. This phenomenon of electromagnetic induction is explained by Michael Faraday's second law of electromagnetic induction, which states that the magnitude of induced EMF is directly proportional to the rate of change in magnetic flux.

So here, we have talked about how current is induced in a conductor and what decides the magnitude of induced EMF in the conductor. But what about the direction of the induced current? In the next video, we will talk about how Lenz's law helps us to find the direction of the induced current in the conductor.