Faraday's law of electromagnetic Induction

Faraday’s Law of Electromagnetic Induction – Principle, Formula & Applications

Michael Faraday (1831) discovered the fundamental principle that governs the working of almost all modern electrical machines — the laws of electromagnetic induction. These laws explain how an EMF (electromotive force) is generated in a conductor whenever there is a change in magnetic flux linked with it.

This principle forms the working basis of:

• Induction Motors

• Generators

• Transformers

• Inductors

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Faraday’s Laws of Electromagnetic Induction

1. Faraday’s First Law

Whenever there is a change in magnetic flux linked with a coil, an EMF is induced in the coil. If the circuit is closed, this induced EMF causes a current to flow.

Ways to change the magnetic field in a coil:

1. Moving the magnet towards or away from the coil.

2. Moving the coil into or out of the magnetic field.

3. Changing the area of the coil placed in the magnetic field.

4. Rotating the coil relative to the magnet.

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2. Faraday’s Second Law

The magnitude of induced EMF is directly proportional to the rate of change of magnetic flux linkages of the coil.

$$E = N \frac{d\Phi}{dt}$$

Where:

• $E$ = induced EMF (Volts)

• $N$ = number of turns in the coil

• $\Phi$ = magnetic flux (Weber)

Flux linkage = $N \times \Phi$

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Demonstration of Faraday’s Law

Consider a coil connected to a galvanometer. When a magnet is brought near the coil:

• The galvanometer needle deflects, showing an induced current.

• If the magnet is moved in the opposite direction, the needle deflects in the opposite direction, indicating a change in polarity.

• Faster motion of the magnet produces a larger deflection, showing that induced EMF depends on the rate of change of flux.

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Derivation of Induced EMF

If flux linked with a coil changes from $\Phi_a$ at time $t_a$ to $\Phi_b$ at time $t_b$:

$$\Delta \Phi = \Phi_b - \Phi_a$$

Change in flux linkages:

$$\Delta (N\Phi) = N(\Phi_b - \Phi_a)$$

Rate of change of flux linkage:

$$E = N \frac{d\Phi}{dt}$$

Also,

$$\Phi = B \times A$$

Where,

• $B$ = magnetic field strength (Tesla)

• $A$ = area of the coil (m²)

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Methods to Increase Induced EMF

From the formula, EMF can be increased by:

1. Increasing magnetic field strength (B): Stronger magnetic field → higher flux → higher EMF.

2. Increasing number of turns (N): More turns = proportionally higher EMF.

3. Increasing coil area (A): Larger area links more flux, raising EMF.

4. Increasing relative speed: Faster movement of coil/magnet cuts flux lines at a higher rate.

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Applications of Faraday’s Law

Faraday’s law is the foundation of most electrical machines and devices, including:

• Transformers – energy transfer between circuits.

• Induction Motors – convert electrical energy into mechanical energy.

• Generators – convert mechanical energy into electrical energy.

• Induction Coils – produce high voltage from low voltage supply.

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✅ Conclusion: Faraday’s Law of Electromagnetic Induction is the backbone of electrical engineering. Without it, the modern world of power generation, transmission, and electric machines would not exist.

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