Childrens Illustrated Encyclopedia

ELECTRICITY

182

Basic

generator

ELECTRICITY FROM CHEMICALS

Chemical energy from food changes into movement

in your muscles. Chemical energy can also change into

electrical energy. This is how a battery works. Chemicals

react together inside a battery and produce an electric

current. When there are no

fresh chemicals left, the

current stops. Fuel

cells also produce

electricity from

chemicals in the

form of gases.

BATTERY

Connecting a battery in a circuit

makes the chemicals inside react

to produce an electric current. The

battery provides a force that pushes

electrons around the circuit. The

energy provided by this force is

measured in units called volts.

Inside the battery, the electrons

flow from the positive terminal and

back to the negative terminal.

ELECTRIC MOTOR

Many machines are powered

by an electric motor, which

contains a coil of wire placed

between the poles of a magnet.

The electric current fed to the

motor flows through the coil,

producing a magnetic field.

The magnet pushes on the

coil and makes it spin

around and drive the

shaft of the motor.

ELECTRIC SHOCKS

Living things make use of electricity.

Weak electric signals pass along

the nerves to and from the brain.

These signals operate the muscles,

maintain the heartbeat, and control

the way in which the body works.

A strong electric current can give

an electric shock that damages

the human body and may even

cause death. Never play with an

electricity supply because of the

danger of electric shock.

GENERATOR
Generators produce electricity from the energy of
movement. A coil of wire moves between the poles
of a magnet. This produces an electric current in
the coil. Small, simple generators that power
bicycle lamps are called dynamos. Large
generators in power stations produce huge
amounts of electricity for homes and
factories.

Coil of

wire

A simple generator (above)

contains a coil of wire that

spins between the poles of a

magnet. A current flows

in the coil when it

moves through the

magnetic field.

Instead of a

simple magnet,

there is a set of

electromagnets—coils

that use electricity to

produce a strong

magnetic field.

Electromagnets

spin inside another

set of coils. This

produces

electricity in the

outer set of coils.

The magnetic force

pushes on the coil

and makes it

spin around.

Electric current

flows from

battery into coil,

producing a

magnetic field.

Gears

connect motor

to wheels of car.

Magnet

produces

magnetic field.

Coil of wire

Shaft of motor

In a hydroelectric

power station, water

falling from a dam

spins a turbine.

A shaft
connected to the
turbine (a set of
vanes) drives the
generator.

Magnetic field

produced by

magnet.

ELECTRIC EEL

The rivers of South America

are the home of the electric eel.

This eel has special organs in its long

body that work like batteries to produce electricity.

With a powerful electric shock, the electric eel can stun its prey.

DISCOVERY

About 2,500 years ago, the

Ancient Greeks found that

rubbing amber (fossilized

resin) produces a charge of

static electricity. The Greek

for amber is elektron, which is

how electricity got its name.

Around 1750, American scientist

Benjamin Franklin (left) discovered

that lightning is electricity and

explained what electric charges are. At

the end of the 18th century, Italian

scientists Luigi Galvani and Alessandro

Volta produced the first electric battery.

A bird sitting on an electric cable does

not get an electric shock. The electricity

does not pass into its body because the

bird is touching only one wire and does

not complete an electric circuit.

Benjamin Franklin

(1706-90) studied

the electrical

nature of lightning

by flying a kite

during a

thunderstorm.

Find out more

Atoms and molecules

Electronics

Energy

Fish

Magnetism

Positive

terminal

Powdered

chemicals

react

together

to release

electrons.

Negative

terminal