Faraday's Law

What is Faraday’s Law?

Faraday’s law of electromagnetic induction which is also known as Faraday’s law is the basic law of electromagnetism which explains the working principle of motors, generators, inductors, and electrical transformers. It helps to understand key points leading to the practical generation of electricity or electromagnetic induction.

The law was proposed in the year 1831 by an experimental physicist and chemist named Michael Faraday. So you can see where the name of the law comes from. That being said, the Faraday’s law or laws of electromagnetic induction are basically the results or the observations of the experiments that Faraday conducted. He performed three main experiments to discover the phenomenon of electromagnetic induction.

Faraday’s First Law

Faraday’s first law of electromagnetic induction states that

whenever a conductor is placed in the varying magnetic field, electromagnetic fields are induced known as induced emf. If the conductor circuit is closed, a current is also induced which are called induced current.

Ways of changing the magnetic field

• By rotating the coil relative to the magnet.
• By moving the coil into or out of the magnetic field.
• By changing the area of a coil placed in the magnetic field.
• By moving a magnet towards or away from the coil.

Faraday’s Second Law

Faraday’s second law of electromagnetic induction states that

the induced emf in a coil is equal to the rate of change of flux linkage. Here the flux is nothing but the product of the number of turns in the coil and flux connected with the coil.

Faraday’s Law Formula

The formula of Faraday’s law is given below:

\(\varepsilon =-N\frac{\Delta \phi }{\Delta t}\)

Where,

• ε is the electromotive force
• Φ is the magnetic flux
• N is the number of turns

The negative sign indicates that the direction of the induced emf and change in direction of magnetic fields have opposite signs.

Additionally, there is another key law known as Lenz’s law that describes electromagnetic induction as well.

Faraday’s Experiment

Relationship Between Induced EMF and Flux:

In the first experiment, he proved that when the strength of the magnetic field is varied then only the induced current is produced. An ammeter was connected to a loop of wire; the ammeter deflected when a magnet was moved towards the wire.

In the second experiment, he proved that passing a current through an iron rod would make it electromagnetic. He observed that when there a relative motion exists between the magnet and the coil, an induced electromagnetic force is created. When the magnet was rotated about its axis, no electromotive force was observed but when the magnet was rotated about its own axis then the induced electromotive force was produced. Thus, there was no deflection in the ammeter when the magnet was held stationary.

While conducting the third experiment, he recorded that galvanometer did not show any deflection and no induced current was produced in the coil when the coil was moved in a stationary magnetic field. The ammeter deflected in the opposite direction when the magnet was moved away from the loop.

Position of Magnet	Deflection in Galvanometer
Magnet at Rest	No deflection in the galvanometer
The magnet moves towards the coil	Deflection in the galvanometer in one direction
Magnet is held stationary at the same position( near the coil)	No deflection galvanometer
The magnet moves away from the coil	Deflection in galvanometer but in the opposite direction
The magnet held stationary at the same position(away from the coil)	No deflection in the galvanometer

Conclusion:

After conducting all the experiments, Faraday finally concluded that if relative motion existed between a conductor and a magnetic field, the flux linkage with a coil changed and this change in flux produced a voltage across a coil.

Faraday law basically states, “when the magnetic flux or the magnetic field changes with time, the electromotive force is produced”. Additionally, Michael Faraday also formulated two laws on the basis of the above experiments.

Applications of Faraday’s Law

Following are the fields where Faraday’s law find applications:

1. Electrical equipment like transformers works on the basis of Faraday’s law.
2. Induction cooker works on the basis of mutual induction which is the principle of Faraday’s law.
3. By inducing an electromotive force into an electromagnetic flowmeter, the velocity of the fluids is recorded.

Frequently Asked Questions

What is Faraday’s law of mutual induction?

When an emf is produced in a coil because of the change in current in a coupled coil, the effect is called mutual inductance.

What is meant by EMF?

Electromotive force or emf is a measurement of the energy that causes current to flow through a circuit.

Why is Faraday’s law important?

Faraday’s law looks at how changing magnetic fields can cause current to flow in wires.