Fleming’s Left Hand Rule and the Motor Effect

 

When a wire carrying an electric current is moved in a magnetic field of a magnet the magnetic field induced by the wire reacts with the magnetic field of the magnet causing the wire to move outwards. Fleming's left hand rule helps you to predict the movement.

First finger - direction of magnetic field (N-S)

SeCond finger - direction of current (positive to negative)

ThuMb - movements of the wire

When a coil of wire carrying a current is placed in a magnetic field the coil turns.

This is called the motor effect.

The Practical Applications of this Theory

By using the three components:

and the coil of the electro-magnet, a wide range of practical applications are possible.

Electric motors have magnets, a coil, and use electricity to produce movement.

The magnet field of the coil pushes away from the magnetic field in the surrounding magnet, so turning the coil and the motor spindle.

Dynamos - use magnets, a coil and movement to produce electricity in exactly the opposite way to the motor. Small electric motors can be used as dynamos, especially for such things as a model wind generator. Connect a propellor to the motor and a voltmeter to the motor wires. Blow on the propeller and watch the voltage go up.

Loudspeakers use electricity, a coil
and a magnet to make the speaker
cone move.

Microphones can work in the opposite
way using movement caused by sound waves together with a coil and magnet
to produce electricity - which then travels
along a wire, usually via an amplifier,
to a loudspeaker which ........

 

Other practical applications of the electro-magnetic effect are:

and Mag-lev trains - but you can find out more about those if you are really interested.

Contents

History of magnetism, What is a magnet
What do magnets do, Test for a magnet
Magnetic fields
The Earth's magnetic field
Theory of magnetism
Induced magnetism
Magnetic properties of iron and steel
Storing magnets
Making a magnet
Electro-magnets
Primary science applications
Self assessment
Comments, reflections and study action plan