1 of 29 © boardworks ltd 2007

1 of 29 © Boardworks Ltd 2007


What is the link between movement, magnetism and electric

current?

Electromagnetism and movement


Wire in a magnetic field


The direction of the force acting on a wire in an

electromagnetic field can be reversed by:

The direction of the force is therefore relative to both the

direction of the magnetic field and the current.

reversing the current reversing the magnetic field

Changing the direction of the force


It is possible to predict the direction of the force acting on

a wire – its motion – if the direction of the current or the

magnetic field are known. Fleming’s left-hand rule is

used to do this.

Fleming’s left-hand rule

thuMb = Motion

First finger = magnetic Field

seCond finger = Current


Increasing the size of the force


Coil in a magnetic field


The motor effect: true or false?


What are electric motors?

How many items do you own that contain an electric motor?

An electric motor is a device that

converts electrical energy into

mechanical energy to produce a

turning effect.

Most motors are powered using direct

current (DC), which is produced by

cells and batteries.

Motors powered by mains electricity

use alternating current (AC).

These motors use electromagnets

rather than permanent magnets.


How does an electric motor work?


DC electric motor simulation


Would the same strength motor be used in both of these?

How can the strength of an electric motor be increased?

How do we increase motor strength?

increase the strength of the magnet

increase the current flowing through the coil

increase the number of turns on the coil


Inducing current in a wire


It is possible to predict the direction of the induced current

produced by a generator if the direction of the force (or

motion) or the magnetic field are known. Fleming’s right-

hand rule is used to do this.

Fleming’s right-hand rule

First finger = magnetic Field

seCond finger = Current

thuMb = Motion


What is electromagnetic induction?

When current flows through a wire held in a magnetic field,

a force is created that moves the wire.

The opposite is also possible: if a

wire is moved across a magnetic

field, a current is produced. This is

called electromagnetic induction.

Induction also occurs if a magnet is

moved in a coil of wire, or if a coil of

wire rotates in a magnetic field.

In all these methods of inducing a current, the wire and

magnetic field move perpendicular to each other. If they

move parallel to each other, no current is induced.


Inducing current in a coil


A generator is a device that converts mechanical energy

into electrical energy. It is the opposite of an electric motor.

Power stations use generators

to produce electricity on a large

scale. Mechanical energy is

provided by rotating turbines

that can be powered by:

What are generators?

high-pressure steam – in

coal, oil, gas and nuclear

power stations

wind – in wind turbines

falling water – in hydroelectric power stations


How do AC generators work?


AC generator simulation


How can the size of an induced current be increased?

In a power station

generator, an

electromagnet is often

used as this can provide

a stronger magnetic field

than is possible with a

permanent magnet.

Increasing the size of the induced current

increase the speed at which the coil rotates

increase the strength of the magnetic field

increase the number of turns in the coil

increase the total area of the coil.


Factors affecting induced current


Induction: true or false?


alternating current – A current that constantly changes

direction. It is produced by most electrical generators.

commutator – The part of a motor that enables the coil to

rotate using direct current.

direct current – A current that always flows in the same

direction. It is produced by cells and batteries.

generator – A device that converts mechanical energy into

electrical energy.

induction – Generating a current in a wire by moving the

wire in a magnetic field, or by moving a magnet inside a coil.

motor – A device that converts electrical energy into

mechanical energy.

slip rings – The parts of a generator that enable the

rotating coil to produce alternating current.

Glossary


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1 of 29 © boardworks ltd 2007

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