Question

What is electromagnetic induction? Give names of two devices based on it.

Answer 1

Electromagnetic induction is the process by which a change in the magnetic field induces an electric current in a conductor. This phenomenon occurs when a conductor, such as a wire, is exposed to a varying magnetic field. It was first discovered by Michael Faraday in 1831 and is a fundamental principle behind many electrical devices.

Faraday's Law of Induction

The induced electromotive force (EMF) in a circuit is proportional to the rate of change of the magnetic flux passing through the loop:

\[ \text{EMF} = -\frac{d\Phi_B}{dt} \] Where:

• \( \Phi_B \) is the magnetic flux.
• \( \frac{d\Phi_B}{dt} \) is the rate of change of the magnetic flux.

The negative sign in the equation indicates that the induced EMF opposes the change in magnetic flux (according to Lenz's Law).

How does it work?

When a magnetic field around a conductor changes, it causes the free electrons in the conductor to move, creating an electric current. This can be done by:

• Moving a magnet near a coil of wire.
• Changing the strength of the magnetic field near the conductor.
• Moving the conductor through the magnetic field.

Important Terms

• Magnetic Flux: The total magnetic field passing through a given area. \[ \Phi_B = B \cdot A \cdot \cos \theta \] Where:
  • \( B \) is the magnetic field strength.
  • \( A \) is the area the field is passing through.
  • \( \theta \) is the angle between the magnetic field and the normal to the area.
• Induced EMF: The voltage generated in a conductor due to the change in magnetic field.
• Induced Current: The flow of electric charge caused by the induced EMF.

Devices Based on Electromagnetic Induction

1. Electric Generator

An electric generator is a device that converts mechanical energy into electrical energy using the principle of electromagnetic induction. It consists of a coil of wire (armature) that rotates within a magnetic field. As the coil rotates, the magnetic flux changes, inducing an EMF and thus an electric current.

2. Transformer

A transformer is a device used to change the voltage level in alternating current (AC) circuits. It works on the principle of mutual induction between two coils (primary and secondary) wound on a common core. When an alternating current flows through the primary coil, it creates a changing magnetic field, which induces a current in the secondary coil.

Conclusion

Electromagnetic induction is a fundamental concept that drives many electrical devices, from generators to transformers, and plays a key role in the production and distribution of electrical energy. By understanding how magnetic fields interact with conductors, we can harness the power of electromagnetism to generate and control electricity effectively.