Faraday’s Law of Electromagnetic Induction

1. What is Induction?

Electromagnetic induction is the process of generating an electric current in a conductor by changing the magnetic field around it.

It happens in two main ways:

  1. Moving the conductor through a magnetic field (like in a generator).
  2. Changing the strength or direction of the magnetic field around a stationary conductor (like in a transformer).

What is a conductor?

Conductor: A material that allows electric current to flow through it easily because it has many free electrons.

2. Definition

Faraday’s Law states that a change in magnetic flux through a coil induces an electromotive force (EMF) in the coil.
This is the basic principle behind electric generators, transformers, and many types of sensors.

It is based on the fact that a changing magnetic field creates an electric field.

2.1. Visualization

Faraday's Law Example

  • Motional emf (electromotive force), induced by moving a conductor through a magnetic field.
  • Moving a magnet through a coil changes the magnetic flux and induces a voltage.
  • The faster the change in magnetic flux, the greater the induced voltage.

2.2. In Formula Form

E = -N × (ΔΦB / Δt)

Where:

  • E = Induced EMF (in volts, V)
  • N = Number of turns in the coil
  • ΦB = Magnetic flux (in weber, Wb)
  • ΔΦB = Change in magnetic flux
  • Δt = Change in time
  • The minus sign indicates that the induced EMF opposes the change in flux (Lenz’s Law).

2.3. Example

If a coil with N = 50 turns experiences a change in magnetic flux of 0.02 Wb over 0.1 s:

E = -50 × (0.02 / 0.1) = -10 V

The negative sign means the induced EMF opposes the change in magnetic flux.

3. Usage

  • Designing electric generators and motors.
  • Building transformers for voltage conversion.
  • Creating inductive sensors like metal detectors or speed sensors.
  • Understanding induction heating and wireless charging.

4. Limitations

  • Assumes a uniform magnetic field and coil geometry.
  • Real coils have resistance and energy losses due to heat.
  • High-frequency changes can cause additional effects like eddy currents.

5. Video Explanation

video coming soon