In the year 1831, Michael Faraday conducted a few experiments that went about to revolutionize our understanding of nature. Electromagnetic induction has a wide range of applications like the electric generator, induction cooking, wireless charging on the new iPhone, and is even used in the electric guitar!

His first experiment involved the following apparatus and setup:

File:Faraday emf experiment.svg

When the key is switched on, magnetic flux through the right coil changes which creates an induced current in the right coil and the galvanometer deflects.

If you're not sure what magnetic flux means, consider a loop of area A placed in a magnetic field B . Then the magnetic flux through the loop is given by:

$$ \Phi = \int{\vec{B} \cdot \vec{dA}} $$

Faraday continued with this idea that a changing magnetic flux induces current and carried out other experiments such as this one:

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When the magnet is brought close to the coil, The magnetic flux through the circular coil increases which in turn induces current in it.

A quantitative way to express this observation is:

$$ \epsilon = - \frac{d \Phi}{dt} $$

The negative sign indicates the direction of the induced current. The induced current always opposes the flux change. (This is what is Lenz's law). This follows from the law of conservation of energy) . Suppose the induced current was in the opposite direction. Then the magnet would be attracted in the direction of the induced current and a small push would keep it moving forever giving us free energy. But sadly, this is not how nature works.

Let us now look at an important application of Faraday's Principle of electromagnetic induction... the electric guitar.

One of the main components of the electric guitar is the pickup.

 A simplified diagram of a pickup is shown below:

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A wire is wound around a cylindrical magnet which is then connected to an amplifier. The permanent magnet produces a north and south pole in the guitar string. When the guitar string vibrates, there is a changing magnetic flux through the coil which induces current in it. This is then amplified and we hear the sound. Quite amazing isn't it?

The electric guitar which revolutionized rock music works on the basis of Faraday's laws.

So who is the real rock star here? You decide.

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