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Question 2: State Faraday’s law of electromagnetism? Also explain statically and dynamically induced emf with experiments.


Electromagnetic Induction

Electromagnetic induction is the phenomenon in which an induced emf is produced in a circuit when linked by a changing magnetic flux.

Statement of Faraday’s Law

Whenever the magnetic flux Ф linking a circuit is changed, there is an emf induced in the circuit. The magnitude of the induced emf is equal to the negative time rate of the magnetic flux through the circuit. Mathematically,

The negative sign shows the induced emf opposes the cause due to which it is produced.


Consider a current-carrying loop placed in a magnetic field B. If the initial flux is Фi at time t = 0 and the final flux Фf at time t, then

If there are N loops in the coil, then,

From the definition of Faraday’s Law, rate of change of flux is equal to the induced emf,

This is the magnitude of the induced emf. The induced emf always produces a current whose magnetic field opposes the original change in the flux. In order to account for this phenomenon a negative sign is put before the expression.

Factors responsible for Induced emf

From the above equation, it is clear that emf depends upon the rate of change of magnetic flux and the number of turns in the coil. When the magnetic flux is changing fast (increasing or decreasing), the emf produced is larger. When the magnetic flux is constant, no matter how strong it is, emf is not induced in the coil. Similarly, greater the number of turns in the coil increases the amount of emf produced.

Statically and Dynamically induced emfs

emf is induced in a conductor when it is placed in a varying magnetic field. The magnetic field can be varied either by moving the conductor in a stationary magnetic field or the conductor is kept stationary and the magnetic field linking the conductor is changed.

“When the conductor is moved in a stationary magnetic field such that the flux linking the conductor changes in magnitude the emf induced in the conductor is called dynamically induced emf.”

The reason for this name is because the emf is induced in the conductor which is in motion.

Similarly, “the induced emf is called statically induced emf when the conductor is stationary and the magnetic field is moving.”

Again the reason for the name is the conductor is static (stationary).


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