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.
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
- 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.
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