Concept of Electromagnetic Induction

What is Electromagnetic Induction

Electromagnetic induction is the basic principle of operation of transformers, motors and generators. Electromagnetic Induction phenomenon produces a voltage or EMF (Electromotive Force) by placing a conductor in a particular position keeping the magnetic field constant variable, or the magnetic field is held stationary, and the conductor is kept moving. Michael Faraday discovered this Law of Induction in 1830.

Electromagnetic Induction by a Moving Magnet

When a permanent magnet is moved in and out of a coil or a loop of wire, an Electromotive Force or emf, also known as Voltage, is induced in it, and hence a current is produced; Faraday noticed this. So, Michael Faraday eventually discovered a way of producing an electrical current in a circuit by using only the force of a magnetic field rather than batteries. Therefore, this led to a very significant law relating electricity with magnetism, known as Faraday’s Law of Electromagnetic Induction.

Faraday’s Law of Induction

Faraday’s Law of Induction describes how changing magnetic fields generates electric current and, equally, how an electric current produces a magnetic field in a conductor. From the above-mentioned moving magnet description, we can conclude that there exists a relationship between an electrical voltage and a varying magnetic field. Therefore, to which the well-known Faraday’s Law states that “When there exists a relative motion between a conductor and a magnetic field, a voltage is induced in a circuit and the magnitude of this voltage is proportional to the rate of change of the flux”. In other words, Electromagnetic Induction is the procedure to produce Voltage, or a current in a closed circuit, by using magnetic fields.

Basically, there are two laws inside Faraday’s Laws Induction. The induction of emf in a conductor is described in the first law, and the calculation of the emf produced in the conductor is described in the second one.

Faraday’s First Law

An electromotive force is induced when a conductor is placed in a changing magnetic field. If the circuit is closed, a current is generated, which is termed as induced current.

Faraday’s Second Law

The degree of the induced electromotive force in a coil is proportional to the rate of change of magnetic flux linked with the circuit.

Fleming’s Left-Hand Rule and Right-Hand Rule

To determine the direction of motion (in motors) and the direction of induced current (in generators), two rules were presented by John Ambrose Fleming. The rules are termed as:

1.    Fleming’s left-hand rule

Fleming’s left-hand rule concludes that if you stretch your thumb, middle finger and forefinger of your left hand such that they are perpendicular to each other, then the forefinger will represent the direction of the magnetic field, the middle finger will define the direction of the current, and the thumb will point out the direction of the force. Fleming’s Left Hand Rule is applicable for motors.

2.    Fleming’s right-hand rule

The right-hand rule states thatif you stretch your thumb, middle finger and forefinger of your right hand such that they are perpendicular to each other, then the thumb represents the direction of the conductor’s movement. In that case, the direction of a magnetic field is represented by the fore-finger, then the direction of the induced current is represented by the middle finger. This is known as the right-hand rule, and this is applicable for electrical generators.

Applications of Faraday’s Law

  1. Transformers
  2. Induction Cookers
  3. Current Lamps
  4. Wireless Energy Transfer
  5. Electric Generators

Lenz’s Law

One of the elementary laws in electromagnetic induction related to the law of conservation of energy is Lenz’s Law, which is used to determine the path of flow of induced currents. Lenz’s law is derived from Faraday’s law of induction.

This law states that the change causing induced emf will always be opposed by the direction of an induced emf. Likewise, if the magnetic flux is reduced, then the induced emf will compete with this decrease by producing an induced magnetic flux that adds to the original flux.

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