Introduction

• Electromagnetic Induction is the phenomenon of generating an electric current in a conductor by changing the magnetic field around it.

• It was discovered by Michael Faraday in 1831.
• It forms the basis of many devices like electric generators, transformers, and induction coils.

---

Faraday’s Experiments

Michael Faraday conducted the following experiments to discover electromagnetic induction:

1. He moved a magnet towards a coil of wire connected to a galvanometer.
   • The galvanometer showed a deflection, indicating the presence of a current.
2. He moved the magnet away from the coil.
   • The deflection was in the opposite direction, indicating a reverse current.
3. When the magnet was stationary, no current was induced.

Conclusion: A current is induced in a conductor when there is a relative motion between the conductor and a magnetic field.

Principle of Electromagnetic Induction

Electromagnetic induction occurs when:

1. There is a change in magnetic flux linked to a conductor.
2. This changing magnetic flux induces an electromotive force (EMF), which produces an electric current if the circuit is closed.

Magnetic Flux

• Magnetic Flux (Φ\Phi) refers to the total magnetic field passing through a surface.
• It is given by the formula:

Φ=B⋅A⋅cosθ

Where:

• Φ= Magnetic flux (in Weber, Wb)
• B= agnetic field strength (in Tesla, T)
• A = Area of the coil (in m²)
• θ= Angle between the magnetic field and the area vector.

Faraday’s Laws of Electromagnetic Induction

1. First Law: Whenever the magnetic flux linked with a conductor changes, an EMF is induced in the conductor.
2. Second Law: The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux.

EMF ∝ Δt / ΔΦ

Where ΔΦ is the change in magnetic flux and Δt is the time taken for the change.

Lenz’s Law

• Lenz’s Law states that the direction of the induced current is such that it opposes the change in magnetic flux that produced it.
• This is represented mathematically as:

EMF ∝ -( ΔΦ /Δt )

• The negative sign shows opposition to the change in flux.
• Lenz’s Law is a consequence of the law of conservation of energy.

Direction of Induced Current

The direction of the induced current can be determined using Fleming’s Right-Hand Rule:

• Stretch the thumb, forefinger, and middle finger of your right hand at right angles to each other:
  • Forefinger → Direction of the magnetic field.
  • Thumb → Direction of motion of the conductor.
  • Middle finger → Direction of the induced current.

Applications of Electromagnetic Induction

Electromagnetic induction is used in:

• Electric Generators: Converts mechanical energy into electrical energy.

• Transformers: Changes the voltage of alternating current.

• Induction Stoves: Uses changing magnetic fields to heat cooking vessels.

• Electric Bells and Relays.

• Magnetic Braking in trains.

Key Points to Remember

1. Electromagnetic induction is the generation of EMF and current due to changing magnetic flux.
2. Faraday’s Laws and Lenz’s Law govern electromagnetic induction.
3. Fleming’s Right-Hand Rule determines the direction of the induced current.
4. It forms the working principle of generators, transformers, and many electrical devices.