Electromagnetic Induction: Magnetic Flux, Faraday՚S Laws of Induction (For CBSE, ICSE, IAS, NET, NRA 2022)

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  • Induction is a process in which a conductor is put in a particular position and magnetic field keeps varying or magnetic field is stationary and a conductor is moving.
  • This produces a Voltage or EMF (Electromotive Force) across the electrical conductor.
  • Michael Faraday discovered Law of Induction in 1830.
Electromagnetic Induction

The induction of an electromotive force by the motion of a conductor across a magnetic field or by a change in magnetic flux in a magnetic field is called Electromagnetic Induction.

Magnetic Flux

The magnetic flux of a system can be defined through a surface area A and it is placed in a uniform magnetic field B as

The represents the angle between A and B

Faraday՚S Laws of Induction

Faradays Laws of Induction
  • According to this law, the emf induced in a coil of N turns is in direct proportional to the rate of change of flux through it.
  • First law: Whenever a conductor is placed in a varying magnetic field, EMF induces and this emf is called an induced emf and if the conductor is a closed circuit than the induced current flows through it.
  • Second law: The magnitude of the induced EMF is equal to the rate of change of flux linkages.
  • So now, the induced voltage is as follows:
  • where,
  • e is the induced voltage N is the number of turns in the coil Φ is the magnetic flux t is the time

Lenz՚S Law

  • This law states that the polarity of the emf which is induced tends to produce a current opposing to the change in the magnetic flux that produced it.
  • The negative sign represents the opposition.

The Lenzs Law

Eddy Currents

  • By Lenz law of electromagnetic induction, the current swirls in such a way as to create a magnetic field opposing the change.
  • The reason is that the tendency of eddy currents to oppose, eddy currents cause a loss of energy.
  • Eddy currents transform more useful forms of energy, such as kinetic energy, into heat, which isn՚t generally useful.
  • In many applications, the loss of useful energy is not particularly desirable, but there are some practical applications.
  • In nearby metal bodies, changing the magnetic fields can create current loops which get dissipated in the form of heat. These currents are known as eddy current.

Applications of Electromagnetic Induction

  • Electromagnetic induction in AC generator
  • Electrical Transformers
  • Magnetic Flow Meter