65.66_Applications of Electromagnetic Induction

Lesson Objectives

By the end of the lesson learners will be able:

10.4.2.3 – to explain the operating principle of electromagnetic devices (electromagnetic relay, generator and transformer);

Keywords

Voltage and Current Size

The induced Emf,ℇ, (and current, I,) is increased if:

the magnet and/or coil is moved faster (V)
there are more turns (N) on the coil
using a magnet with a stronger field (B)
A coil of several turns instead of a wire is used

Induced Voltage and Inductance

Laws of EM Induction

Size of the voltage

Direction of the voltage

Note Well

An EMF……..When:

The coil is moved through the magnetic field, across the pole pieces.

The magnet is moved so that the wire passes across the face of the pole pieces.

The wire is held stationary between the pole-pieces.

The magnet is moved so that the pole –pieces move along the length of the wire

The wire moves lengthways so that it does not change its position between the poles of the magnet.

Activity

Explain the applications of electromagnetic induction in:
Electromagnetic relay
Simple generator
Transformer
Metal detector

Fleming’s Left and Right Hand Rules

E = B L v

If the wingspan is L
E = B L v cos θ

Sound waves strike the diaphragm making it vibrate at the same frequency as the sound.The moving diaphragm moves the coil backwards and forwardswhich induces a changing current at the same frequency as the sound.