Electromagnetic induction

Faraday’s laws is the basic law of electromagnetism that helps us to predict how a field (magnetic) would interact with a circuit to produce an EMF. This is known as electromagnetic induction.

Faraday proposed the laws of electromagnetic induction in the year 1831. Faraday’s law or the law of electromagnetic induction is the results of his experiments. Faraday performed three experiments to discover the phenomenon of electromagnetic induction.

Any change in the magnetic environment of a coil of wire will cause production of emf in the coil. No matter how the change is produced, an EMF would be generated.

Electromagnetic Induction

Electromagnetic Induction is a process in which

1. A conductor is put in a particular position and magnetic field keeps varying
2. The magnetic field is stationary and a conductor is moving.

This produces electromotive force across the electrical conductor.

Michael Faraday discovered the Law of Induction in 1830.

Electromagnetic induction is the induction of an EMF by a conductor moving across a magnetic field or a change in magnetic flux in a magnetic field.

This occurs when a conductor is placed in a moving magnetic field, when an AC power source is used, or when a conductor is constantly moving in a stationary magnetic field.

Michael Faraday discovered this electromagnetic induction law. He built up a leading wire, which he linked to a device that measured the voltage across the circuit. The voltage in the circuit is measured when a bar magnet passes through the circuit. The significance of this is that it is a method of producing electrical energy in a circuit by employing magnetic fields rather than batteries. Electromagnetic induction is used in machinery such as generators, transformers, and motors.

Faraday’s law of Electromagnetic Induction

First law

When a conductor is put in a changing magnetic field, an induced emf is produced, and if the conductor is a closed circuit, an induced current flows through it.

Second law

It states that the magnitude of the induced electromagnetic field is equal to the rate of change of flux.

Formula for Electromagnetic Induction

Faraday’s law of electromagnetic induction, based on his experiments, states that the amount of voltage induced in a coil is proportionate to the number of turns and the changing magnetic field of the coil.

We can now deduce the formula,

e= N × dΦ/dt

Here,

e= Induced Voltage

N = number of turns in the coil

Φ = magnetic flux

t= time

Lenz’s law of Electromagnetic Induction

When an emf induces according to Faraday’s law, the polarity (direction) of that induced emf opposes the cause of its generation. This is the Lenz law of electromagnetic induction.

Formula for Lenz’s Law is the following:

E = -N (dΦ/ dt)

 Eddy currents

The current swirls in such a way that it creates a magnetic field that opposes the change. This is the Lenz law of electromagnetic induction. Eddy currents waste energy because they have a tendency to oppose one another. Eddy currents convert more usable kinds of energy like kinetic energy into heat, which isn’t always useful. Although the loss of usable energy is undesirable in many applications, it does have some beneficial applications.

•       In the brakes of some trains. The brakes expose the metal wheels to a magnetic field during braking, which causes eddy currents to form in the wheels. The wheels are slowed by the magnetic interaction between the applied field and the eddy currents. The impact is larger the quicker the wheels spin, thus as the train slows down, the braking force decreases, resulting in a smooth stop.
•       Few galvanometers with a fixed core made of nonmagnetic metallic material exist. When the coil oscillates, the core’s eddy currents oppose the motion and bring the coil to a stop.
•       The melting of metals in an induction furnace can be used to make alloys. The metals’ eddy currents generate extremely high temperatures.

Applications of Electromagnetic Induction

Electromagnetic induction in AC generators & Electrical Transformers are some of the uses.

Electromagnetic induction in AC generator

A more advanced equipment is the AC generator with a 100 MV output capacity.  The effective area of the loop when the coil rotates in a magnetic field B equals A cosθ, where θ is the angle between A and B. The operating principle of a basic ac generator is this approach of producing a flux change. The axis of the spinning coil is perpendicular to the magnetic field direction. The magnetic flux through the coil changes as the coil rotates, causing an emf to induct in the coil.

Electrical Transformers

An electrical transformer is another key application of electromagnetic induction. A transformer is a device that uses a magnetic field to shift ac electric power from one voltage level to another. The voltage in the primary of a step-down transformer is higher than the voltage in the secondary. A step-up transformer is one in which the secondary voltage has additional turns. To enhance the voltage to 100 kV, power companies utilise a step transformer, which reduces current and reduces power loss in transmission lines. Household circuits, on the other hand, use step-down transformers to reduce the voltage to 120 or 240 V.

Conclusion

After conducting all of the tests, Faraday came to the conclusion that if a conductor and a magnetic field were in relative motion, the flux coupling with a coil changed, and this change in flux created a voltage across a coil.

The electromotive force is produced when the magnetic flux or magnetic field varies with time, according to Faraday’s law. On the basis of the preceding experiments, Michael Faraday also created the above famous two laws.