How Things Work Encyclopedia

Gases and liquids

Roller coaster Some older roller coasters run on intricate
wooden scaffolding.
These rip-roaring rides are powered
by gravity itself. They slingshot Over the top
thrill-seeking passengers along At the top of a hill,
at breathtaking speeds. roller-coaster cars have
high potential energy.
Going up... There is maximum This becomes kinetic
potential energy at
As the roller coaster goes the top of the hill. energy as the
up the first, tallest hill roller coaster rolls
(called the lift hill), it’s
gradually building down the slope.
up potential energy. arghhh

Rushing down a steep The cars gain speed
slope can make you as they roll down
feel almost weightless, the hill.
which may be quite
uncomfortable!

Chain reaction Where was the world’s first roller coaster?
Roller-coaster cars don’t
have motors. They’re
pulled to the top of the
first hill by a chain
connected to a motor

at the top.

50

Wheeeeeeee! Shoulder Roller coaster
Lots of different things harness
affect the way you feel Flexible metal
when you’re whizzing The tracks and supports
around a roller coaster. of most roller coasters are
made from hollow steel.
Acceleration force This can be shaped into
Apparent weight loops and corkscrews.
Gravity (weight)
Safety first
After coming down the All riders are protected by a
first hill, the cars have safety harness. Brakes are built
enough speed to send them into the track, not the cars—
around the next loop. This they are used at the end
creates “g-force,” which of the ride, or in emergencies.

makes the passengers Cars lose momentum
feel much heavier. throughout the ride,
so the hills have to
get smaller.

There is maximum
kinetic energy at the
bottom of the hill.

Focus the force Ultimate experience
The roller coaster track acts as a channel for Thrill seekers in Florida can enjoy the new
gravity. When the track slopes down, the Rip Ride Rockit roller coaster. It’s very short
car fronts go faster—when it tilts up, the and powerful, so it can pivot like a
skateboard and climb straight uphill.
car backs are pulled
down, and they Passengers can choose
go slower. the music they hear
while they’re terrified.
Steel track
51
Load wheels

Guide wheels

Upstop wheels

Roller-coaster cars are
clamped securely to the
rails by three sets of wheels.

The very first coaster was an elaborate ice slide built in Russia during the 1600s.

Gases and liquids

How do planes fly?

Huge, heavy machines seem to defy gravity by staying up
in the air! Yet airplanes fly around the world every day.
It’s because they can create the forces they need to fly.

The forces of flight Cockpit

“Aerodynamics” means “the way air moves.” There
are four aerodynamic forces—thrust and drag, and
lift and weight. Airplanes need to
balance them out in order to fly.

Thrusting forward Thrust Engine
Planes need to create Propeller
thrust to balance out
drag. This plane has
a propeller to create
thrust. As the
propeller turns, it
draws air past the
blades, pulling the
plane forward.

Cooler air Level of plane A bumpy ride The biggest jumbo
Just like boats bounce The world’s largest plane is the
52 Warmer air rises over waves, planes Airbus A380. At 239½ ft (73 m)
faster, “bumping” can bounce up and long, this jumbo jet can carry up
the plane upward down in the air. to 853 passengers. It’s 10 times
Called turbulence, longer than the four-seater
this happens when Cessna 400.
pockets of air move
at different speeds. Cessna 400
It can be caused by
strong winds, storms, Airbus A380
or when cold and
warm air meet.

What was the first airplane to stay up in the air successfully?

As the plane moves, Weight Lifting up How do planes fly?
air flows over its Lift Lift is the opposite force
wings. The top of to weight. A plane What does that part do?
the wing is curved, creates most of its lift Every part of a plane has a
making the air with its wings. job to do, from the streamlined
above the wing nose to the tail fin that keeps
move faster than the The slow-moving air the plane steady in the sky.
air under the wing. under the wing pushes
up more than the Flaps that come down from the
Airflow fast-moving air above wings are used to increase lift
the wing pushes down. during takeoff and landing.
This creates lift.

Tail fin Ailerons on the back edge
of the wings are used to
Aileron “roll” the plane, to make it
turn or keep it level.

Fuselage

Wing Flap Elevator Rudder A rudder in the plane’s tail turns
the plane left or right.
Drag

Weighing down Dragging back Elevators in the tail move up and
Weight is caused by Drag is the opposite force down to balance the position of
gravity pulling down on from thrust—it slows things the nose, keeping the plane level.
an object. Everything down. Imagine trailing your
has weight, even air. hand in water as you sail 53
The Airbus A380 needs along in a boat. You can feel
to create a lot of lift to the water push back, or
balance out its weight— drag, against your hand. Air
it’s a whopping 617 tons has the same effect on planes
(560 metric tons). (and anything else that
moves). A plane’s smooth
surface and streamlined
shape help to reduce drag.

The Wright Flyer. On its first outing in 1903, it flew for 12 seconds!

Gases and liquids Blastoff!

Nose cone Space is the final frontier. So far,
Command module man has explored only a tiny part
Service module
Rocket stage containing lunar of our galaxy, and this has
module been very difficult, dangerous,
Instrument unit and expensive to do.
Rocket stage
containing fuel What makes rockets go?
Engine
Most rockets need two different
Rocket stage chemicals: a fuel and an oxidizer.
containing fuel When they’re mixed together, they
cause a fierce but smooth burn—this is
Engines funneled downward, propelling the rocket
up. Clamps hold it down while the power
Rocket stage builds, so it doesn’t go end over end and
crash. At the word “blastoff,” the
clamps are removed and the rocket is on
its way. Good luck!

Thrust

When the Apollo lunar-missionGravity
crew returned to Earth, they

landed in the Pacific Ocean and
were rescued by Navy personnel.

54
When was the first liquid-fueled rocket made?

Blastoff!

Shuttle spacecraft Space journey
have a winged After rockets are launched, they use huge amounts
orbiter, a huge of fuel to get into Earth’s orbit. They then release
fuel tank several rocket stages containing fuel so that only
underneath, and the much smaller capsule actually goes into orbit.
two rocket
boosters that 3 Orbit
send them into
orbit. The engines have 4
boosted the capsule
2 into orbit.

As the fuel is Capsule circles
used up, the the Earth in
fuel tanks are orbit.
released.

1Rocket blasts

off from
launch pad.

Command module 7
parachutes into
the ocean.

6
Command
module positions
itself to reenter
Earth’s atmosphere.

5 Space junk
Experts believe there are more
Command module than 150,000 objects orbiting the
separates from Earth—pieces off satellites, bags of
service module.
garbage, and dropped tools.

March 1926, by Dr. Robert H. Goddard in Massachusetts. 55

What is energy?

What is energy?

Energy is what makes everything happen. It is involved in
every action that we make. It powers your muscles, runs
your car, and lights your home. Without energy you could
not ride a bike, watch television, or fly in an airplane.

Different types of energy

Energy can’t be made, just changed from one type
to another. Here are some of the main types.

Light
is a form of energy that we can see.
Most of the energy on Earth comes
from the Sun as light.

Heat energy Atoms vibrate
is the energy of atoms or molecules as they get hotter.
vibrating. The hotter an object
gets, the faster and more violently
the atoms or molecules vibrate.

Nuclear energy
is stored in atoms. Nuclear energy is
used to run power plants that
generate electricity.

Electromagnetic energy
is carried by X-rays, radio
waves, and microwaves.

56
Everything is made up of atoms—but what are they?

What is energy?
Curiosity quiz

Look through the “What
is energy?” pages and
see if you can identify
the picture clues below.

Gravitational energy
is the stored energy in an object that has been lifted but is
not allowed to fall. Dams can turn gravitational energy
into electrical energy.

Kinetic energy
is the energy a moving object has.
The faster a car moves, the more

kinetic energy
it has.

Electrical energy
can travel easily
through wires. It
is the energy we
use to power
devices in our
homes.

Become
an expert...

on power plants,
pages 62–63

on gravity,
pages 44–45

The smallest particles that something can be broken down into. 57

What is energy?

It’s electric!

If you flip a switch to make something Plugs have
work, it probably runs on electricity. metal prongs
Most of the energy we use every day that connect
is electric. with the power
supply wired
What is electricity? Weird or what into the wall.

This magical power source comes Electrical energy Electric sockets are live. You
from electrons—tiny charged travels very quickly, at should never put your finger
particles on the outside of atoms. 125,000 miles (200,000 or an object (other than a
They move from atom to atom km) per second. That’s plug) into a socket—you
creating electrical energy, and this two-thirds as fast as the might get an electric shock.
energy travels on a circuit.
fastest thing ever—
light!
?
Starting small Electricity passes freely
Electrons carry anTo understand electricity, youfrom the socket to the
have to look at the teeny tiny lamp through the wiring.
Electricity flows this waybuilding blocks that everything
is made from—atoms.

Atom

Electrons electrical charge.

Electricity is passed along When you
wires by electrons. When you switch on a lamp,
supply energy to the wire, it electric current
makes the electrons move flows along the
along it, carrying electric flex to the bulb,
charge with them. lighting it up.

58
Who made the first battery?

Simple circuit It’s electric!

A flashlight works using a simple electrical circuit. Electricity
Batteries produce electricity, which flows around
the circuit to power the bulb so it lights up. When we talk about
electricity, we use the
Lamp filament When the switch is on same words over and
“off,” the circuit is broken over again.
and the bulb goes out.
Conductor—a material
that allows electricity to
flow through it easily.

Broken Circuit—a path that an
circuit electrical current can
flow along.

V Voltage—a measure
of electrical strength.

Off On Plastic A Ampere—a basic unit of
case electrical current.
To turn off the
flashlight the Batteries Current—a flow of
circuit is broken. electricity through a
conductor.

Slide switch Power masts
Electricity travels from power
When the switch slides to plants along thick cables often
“on,” the circuit is complete strung between big metal towers.
and current flows all the way The cables carry very high levels of
to the bulb, which lights up. electricity—enough to kill an adult
man if they fell on him.

Off

Metal switch Birds don’t complete an electrical
contacts circuit with the ground like people
do, so they can sit on cables
Metal spring without being harmed.

Electricity flows from the batteries
and along the metal wire.

An Italian named Alessandro Volta made the first battery in 1800. 59

What is energy?

The power of magnets

Magnets create an invisible force known as

magnetism that repels and attracts certain

BEWARE: substances, like iron. Electricity and
ELECTRICAL CHARGE!
magnetism have a close relationship.

Can you field the force? Iron filings reveal the magnetic field around a magnet
A magnetic field is the
space around a magnet Poles N S
where its force can be felt.
The force gets weaker as NS Opposite poles attract
the field gets farther from
the magnet. It is strongest
at the two poles.

Magnetic Earth SS Magnets have two points where their field is
strongest, known as poles. Each magnet has
The Earth acts like a gigantic Similar poles repel a north and south pole. These can attract
magnet. It has a magnetic north and repel other magnets. Similar poles repel
and south pole, although they and opposites attract.
aren’t in the same place as the
geographical poles, but are very Super magnets
close. Over the Earth’s lifetime These are really sticky
the magnetic poles have magnets. They can be
switched around a few times. natural magnets or
electromagnets.

The maglev train uses an

N electromagnet.

E

NW

S

A compass uses a

S magnet as a “needle.”
The needle is attracted
and points to the
magnetic north pole.

60
Which elements are attracted to magnets?

The power of magnets

Electromagnets Everyday magnets
A magnet can produce
electricity and electricity can Magnets are used in many everyday items,
create magnetism. An iron such as:
bar can become magnetic
when an electric wire is Audio speakers use Credit cards use a
wound around it in a coil. electromagnets to make magnetic strip to store
A moving magnet can also sound vibrations. your information.
make an electric current in a
coil of wire. Electromagnetic Some handbags Central locking in a
generators are used to create close with magnetic car uses a series of
electricity at power plants. clasps. electromagnets to lock up.

The wheel has to keep turning for
the dynamo to light the bulb.

Wheel power
A simple example of an electromagnetic generator is
a bicycle dynamo. It uses the kinetic energy produced
by the spinning wheel to turn the magnet past a coil
of wire. The movement of the magnetic field produces
enough electric current to light a bicycle light.

Electric current runs up the
wire to power the light bulb.

Wheel spins

The dynamo turns weird or what?
as the wheel spins.
Lodestone is a naturally
The magnet occurring magnet thought to
rotates. be made when lightning strikes.
In 500 BCE Thales of Miletus
Iron core noticed it because the iron

Coil of insulated nails in his sandals
wire surrounds stuck to it.
the iron core.

Electrical output The insulated wire stops the
current from taking a shortcut
from loop to loop and keeps
it flowing around the core.

Iron (Fe), Nickel (Ni), and Cobalt (Co) are all attracted to magnets. 61

What is energy? In Shanghai, China, vast quantities of coal are loaded
on a conveyor belt.
Power plants

There are two kinds of energy—
renewable and nonrenewable.
Earth will run out of non-
renewable fuels, but renewable
energy comes from endless
resources such as wind and sun.

Burn, burn, burn

Most power plants burn nonrenewable

fossil fuels like coal, oil, and natural gas.

These are formed from fossilized plankton

Smoke and hot or plants that lived millions of years ago.
gases escape from
the chimney. Fossil fuels release energy from these plants

Heat from burning when they’re burned.
coal turns water
in the pipe into Flow of The steam drives The turbines produce
steam. Ash collects steam the turbine. electricity by turning a
underneath. magnet inside a large
coil of wire.

Pump Cooling
water out

The steam
passes into
a condenser.

Crushed coal Ash Pump brings
and hot air in cooling
As the steam water.
condenses to

water, it collects

in this tank. Cold water in

the pipe cools

the steam so

Flow of water it condenses.

62
How far does power travel?

Power plants

Dangerous power Green power
Nuclear power plants create energy by splitting uranium
atoms, which release heat to run the generators that Renewable energy sources
make electricity. Nuclear power is nonrenewable will always be there—
because there is a limited supply of nuclear fuels. The and they’re less harmful
waste from these fuels is radioactive, so they may to the environment than
damage cells and cause cancer. fossil fuels.

On April 26, 1986, at Solar power comes from
1:23 a.m., Reactor Four the Sun. In theory, it could
at Chernobyl Nuclear provide all our energy.
Power Plant in Ukraine
exploded. Over 20 years Hydroelectric power is
later, an inspector checks created by falling water,
the interior (left). like a dam or waterfall.

Transformer Become Wind power is generated
“steps up” the an by turbines. Lots of them
voltage. together make a wind farm.
expert...
Tidal power uses water in
on renewable the form of waves rather
energy, than waterfalls.

pages 66-67

Stretched between Power masts are huge Biofuels (like corn oil) are
towers, cables carry steel towers. They made from growing things,
have extra wires so they’re renewable.
high currents. running along the top
to ground lightning. Geothermal power comes
from heat deep, deep down
toward the Earth’s core.

Substations reduce Electricity is wired
voltage and send power to power points in
in different directions. your home. It
connects with
On the Local grid equipment through
way... a plug.
All over the Cables below
world, rows of ground 63
masts march across
the landscape. They
support the high-tension
cables that carry electricity
from power plants to homes
and offices.

Power can travel up to 300 miles (480 km) to your home.

What is energy? What can you do
to save energy?
Running out

Most of the energy we use comes Grow your own fruit and
from burning fossil fuels. But these vegetables. Try to eat food
fuel sources won’t last forever, so we that is produced locally.
need to start thinking about how we
can use less energy, and try to find Don’t waste heat. Ask
other ways of providing it. your parents to make sure
your home is insulated.

Save gasoline. When you
can, walk instead of
asking for a ride.

Turbines in a coal-fired power plant Steam power Turn off your television
without their metal covers. Electricity that comes and computer. Don’t leave
from coal is relatively them on standby!
inexpensive to make. In a
machine called a pulverizer, Switch off lights when
the coal is broken down into you leave a room, and use
a fine powder, then burned energy-saving light bulbs.
in a furnace. The furnace
heats a boiler to produce Dry laundry outside
steam. The steam powers instead of using a dryer.
turbines that run generators
to create electricity. Recycle and reuse items
such as glass, plastic,
Tall pipes are used to and paper.
drill oil from the
ocean floor. Oil rig

Oil and gas Marine life that Oil reservoir
We get oil by drilling has decayed.
under the ground— A layer of rock traps the
from dry land, or from decaying remains, which
the ocean floor. Today, turn into oil.
we use oil for 38
percent of our energy, How much oil can the largest oil rig store?
either as fuel for
heating, or turned into
gasoline for cars and
planes. Experts think
oil reserves will run
out in about 40 years.

64

Running out

Compressed lignite weird or what?
turns into coal.
In the US, about
half of all the

electricity used comes
from coal-burning
power plants.

Compressed peat Black diamonds
becomes lignite. Like diamonds, coal is a form of
carbon. Excavated from the
Decaying plants ground through deep mines or open
form peat. pits, it provides 25 percent of the
world’s energy supply. If we
Peat is the earliest Underground gas continue digging coal at the
stage in the Natural gas is also a fossil current rate, we have about a 250
formation of coal. fuel. It comes from coal beds, years’ supply left in the Earth.
marshes, bogs, and oil reserves.
The largest reserves of natural Gas facts
gas are shared between Iran and Easily piped into
Qatar, although Russia is the homes, natural gas is
world’s biggest gas producer. completely clear and odorless.
Natural gas is likely to run out When it burns, it releases lots of
in about 100 years. At the energy, which makes it suitable
moment, it provides 23 percent for use in cooking, heating, and
of our energy. cooling. It also gives off fewer
harmful substances than
other fossil fuels, so it’s
slightly greener.

The Hibernia platform in the Atlantic Ocean can hold 1.3 million barrels of crude oil. 65

What is energy? Become
an
Renewable energy
expert...
Energy made from fossil fuels will
eventually run out, but certain on energy-efficient
types of energy are renewable, homes, 72–73
which means that we can go on
using them forever. Low-speed Anemometer
shaft Controller

Gear box

The wind
blows the
blades
around.

Brake One hundred people could fit on one blade.Generator

Wind farms are where lots of turbines are Blade High-speed
installed in a field or in the sea. shaft

Electricity is wired
to power points in
your home.

Substations divide
power so it can travel
in different directions.

Local grid

Cables carry high Wind power Wind moves
currents between Wind turbines use the power of moving faster the
masts. air currents to spin their propellers. These higher up
are huge windmill-like blades on top of a you go from
The transformer tall tower. As they spin, generators inside the ground.
sends alternating the turbines make electricity, which is Taller towers
currents into sent via cables underground. generate
power lines. more
electricity.
The electricity travels underground
Underground
66 to a transformer station.
When was the first geothermal plant built?

The spillway of a dam Renewable energy
is used to control the
Hydroelectric power
flow of water. A fifth of the world’s electricity comes from
hydroelectric power plants. Usually a dam is
Water from built to trap a river and create a lake. Water is
a reservoir released at a controlled rate and allowed to
flows down flow through a spinning machine called a
a pipe to a turbine, which drives an electricity generator.
turbine.
Solar energy
Electricity Huge glass panels are put on the
generator roofs of buildings to capture energy
from the Sun and convert it into
electricity. The stronger
the sunlight, the more
electricity they make.

Turbine When sunlight lands Solar panel
on a cell, electrons
Geothermal energy are pushed from Photovoltaic
The Earth’s crust is a hot one layer to the cell
place! Some rocks can be as other creating an
hot as 1,800 ºF (1,000 ºC). electric current. Pure silicon doesn’t conduct electricity
Geothermal energy uses well. Each cell contains silicon doped
the heat from these rocks (made impure) with phosphorus,
to generate electricity which produces free electrons.
and heat water.
Silicon doped with boron makes “holes”
One of the biggest where electrons are missing in the cell.
geothermal areas in the
world is Iceland. People Biofuels
can swim next door to Biofuels come from fast-growing crops,
this geothermal plant in such as corn, sugar cane, and palm oil.
Iceland since the water These fuels can add to or replace fossil
is so warm. fuels such as diesel or gas. Biofuels have
been criticized for taking up land that
could be used to grow food.

The first plant was built in 1904 in Ladarello, Italy. 67

What is energy?

What’s cooking?

The stove is probably the most important
piece of equipment in the kitchen. Without
it, you’d have to eat all your food raw.

Heat is a form The oven
of energy. It
comes from the Inside an electric oven are large coils of wire called
movement of heating elements. These heat up when electricity
atoms and travels through them. They are controlled by
molecules. a thermostat that keeps
The faster the the temperature
molecules move inside constant.
around, the
higher the On a burner, the
temperature. element is in direct
contact with the
Dial controlling saucepan, which
the thermostat. passes the heat
through to
the food.

Because the broiler Convection ovens
element is much closer to have fans that blow
the food and gets hotter air around and keep
than the one in the oven, the whole oven at the
the food cooks quickly. same temperature.
Food cooks faster in
a convection oven.

The oven works by
surrounding the food
with hot air. Since hot air
rises, the top of the oven
is slightly hotter than the
bottom. When the oven
gets too hot, the
thermostat turns the
heating elements off. It
turns them back on again
when the oven cools.

68
Can you cook ice cream in an oven without melting it?

What’s cooking?

Heat’s effect on food

Heat changes food, and different foods react to it differently.
Cooking is simply delicious experiments in chemistry and physics.

Cooking eggs Baking bread Sweet treats
Egg whites and yolks are A basic bread mixture includes Many candies are made
made of stringy chains of flour, water, and yeast. Yeast by simply adding sugar
protein floating in water. is a live, single-celled fungus. to water and heating the
Flour, when it mixes with mixture to very high
Chains of water, releases stretchy gluten. temperatures.
protein
++ +

Each individual chain Yeast is inactive until it comes As you cook it, the water
into contact with warm water. boils away, leaving a much
is twisted and curled up. When the bread mix is left in stronger solution of sugar.
a warm place, the yeast starts Very strong solutions make
When you add heat, the feeding on the sugars in flour toffee or hard tack candy.
and releases carbon dioxide gas.
chains uncurl and start

to link together. Chains of

protein
unravel and

join up.

Gas is Water
released. boils out
of the
sugar.

The chains form a mesh The gumlike gluten fills with If you stir the mixture as it
that traps the water they thousands of gas bubbles and cools, it forms crystals. This
floated in. The egg the bread rises. Cooking traps is how you make fudge, but
is now cooked. the bubbles in the bread. you leave hard candy to set
without stirring.

The chains 69
form a mesh.

Yes, if you make baked Alaska—ice cream covered in meringue.!

What is energy?

Keeping cool

We keep food cool so it stays fresh, Eggs are usually stored in
and we keep liquids cool so they’re the refrigerator door,
refreshing to drink. Electricity which is a few degrees
makes all this possible. warmer than the shelves.

45ºF Some foods don’t need to be Room temperature
(7ºC) and chilled to stay fresh. Dry foods such as beans
and pasta keep very well
above at room temperature. Lettuce and other
Root vegetables like salad vegetables go
potatoes don’t need to in the door, or in a
be refrigerated, but they drawer at the bottom
keep best in a cool of the refrigerator.
place rather than a
warm one.

32–45ºF Let cheese Refrigerator Cool coil
(0–7ºC) warm up The temperature inside
before you a refrigerator is cold
32ºF eat it. enough to slow down
(0ºC) and the growth of bacteria
(germs) in our food, so it A long coiled
below stays fresh longer. Dairy
products, meat, and pipe is set into
70 fish should always be
stored here. the refrigerator

walls. Inside is a

gas called

tetrafluoroethane,

which travels

around the fridge

Some treats and Freezer soaking up heat.
desserts are Freezers are cold enough
served frozen. to make your skin freeze! This heat travels
Bacteria can’t multiply
in these temperatures, to a compressor,
so food stays fresh for
months or even years. and is then
Most foods are thawed
or warmed before you released at the Gas
eat them. back, which coolant
is why it feels circulating
warm there. around
fridge

How quickly do bacteria grow at room temperature?

Keeping cool

Adjustable
temperature
control

Warmed Compressor
coolant
Control
Compressor electronics

In just four hours, one bacterium can turn into more than 1,000! 71

What is energy?

Energy efficiency

Every home needs energy for heating, lighting, cooking,
and lots of other things. It’s important not to waste this
power—not only because you have to pay for it, but also
because the sources of this power may one day run out.

Eco living The windcatcher Triple-paned windows have
channels air into three panes of glass with a
Sustainable homes are the house, providing layer of air between them.
designed to be better for ventilation. The The air stops heat from
the environment. They aluminum tubing escaping, so you need less
have lots of features that reflects light inside. energy to heat the house.
save energy and water.
They produce fewer
carbon emissions and
are also cheaper to run.

The outside of the roof is
covered in photo-voltaic and
solar panels. These generate
electricity for the whole house.

The “Lighthouse” is

built with materials

that absorb heat A biomass boiler burns wood

during the day and pellets for heating and hot

72 give it out at night. water during the winter.

What are carbon emissions?

In your home Energy efficiency
We can all do things to
make our homes more energy Batteries
efficient. A lot of energy is used
to heat a house. Ask your Every household uses
parents to lag your attic with batteries to power all
insulation to keep heat in. You kinds of things—but
can also insulate walls and batteries eventually run
floors, plug gaps around doors out. So how should you
and windows, and install dispose of them?
double-paned windows.
Change old batteries
Thermograms are Insulating a loft right away. Batteries
pictures that show contain chemicals that may
hot things as white Become leak and ruin the gadget.
and yellow and an expert...
cold things as blue. Don’t trash batteries.
The hottest part of Recycle them instead—it’s
this house is its better for the environment.
windows, because
heat is escaping Batteries should never
through them. be thrown onto a fire—
they might explode.

When rain hits the roof, on saving energy,
it collects in a gutter and pages 64–65
runs down a pipe into a
recycling tank. The water is on renewable energy,
used in a washing machine. pages 66–67

When things break… Make a difference
However energy-efficient you are, electrical If you get a new computer or cell
goods will eventually wear out. But some phone but there’s nothing wrong
items are simply too dangerous to throw with the one you had, you can
away. Old refrigerators contain gases that donate the old one to charity. Go
are harmful if they leak. The safest way to online to find charities, schools,
get rid of a broken refrigerator is to contact and groups that can make good
your local recycling center. use of your unwanted equipment.

Broken fridges 73
must be taken
apart carefully
so they don’t
release harmful

gases.

Gases containing carbon that are released into the air and may cause global warming.

Light and sound

Light and sound

A glass prism splits the light into colors. un’s atoms give out lots ofMost of what we know about the
world we learn by seeing and hearing.
See the light Everything we see needs light, and
Light is made up of different everything we hear involves sound.
colors, but light cannot be They can both reach us by traveling
seen unless it hits our eyes. in waves.light.
Light travels in straight lines,
but it can change direction. What is light?
When light passes through a
prism (usually a three- Light is a type of energy called
dimensional glass triangle), electromagnetic radiation, or EMR.
it bounces off the sides of “Electromagnetic” means it’s made up
the prism and bends. Some of electrical and magnetic energy, and
colors in light bend more “radiation” means it spreads out from
than others, so they spread a source. Atoms—the tiny particles
out and you can see the that make up everything around us—
different colors. are that source. Atoms that have too

much energy can get rid of it
in the form of light.
The S

The speed of light Light doesn’t always behave like a wave.
Light travels in waves, a bit like waves that travel through Sometimes it behaves like it’s made up
water. Light travels faster than anything else in the universe— of particles, so it spreads out more like
an amazing 186,000 miles per second (300,000 km per second)! a spray of water from a hose than
It takes just eight minutes for light from the Sun to reach Earth. waves in the sea.

74
What is refraction?

Secrets of sound Light and sound

When something vibrates, it Curiosity quiz
squeezes and stretches the air
around it, sending out waves Look through the “Light
that we hear as sound. and sound” pages and
see if you can identify
Echolocation the picture clues below.
Some animals use sound
to find their way around.
This is called echolocation.
Bats send out high-pitched
squeaks that bounce off their
surroundings. If their echo
comes back quickly, it means
there’s something nearby.

Cymbals make
large waves,
which means
a loud sound!

The speed of sound

Sound travels more slowly than light, at 1,125 ft per second

(343 meters per second) in air. But the speed changes,

depending on what the waves are traveling through.

They can move four times faster in water than in air. Become

an expert...

on visible light,
pages 76–77

on how ears hear,
pages 90–91

Refraction is when light waves bend, such as in a prism. 75

Light and sound

Now you see it…

Light waves (or electromagnetic Blue

waves) are all different

lengths, but each length Cyan

travels at the same speed.
Some light waves are too short Green

or too long for us to see.
The light we can see is called Red

“visible spectrum” light. Light of many colors

... And now you don’t Visible light is made up of waves of
different lengths. Each length appears
Our eyes can see only light waves of as a separate color. For example, red

a certain size—if they’re longer or waves are long and blue rays are
shorter, they’re invisible. We use short. Light contains an endless
invisible electromagnetic waves in amount of colors. The only limit is
our lives every day. on how well your eye and brain can
tell one wavelength from another.

Radio waves Microwaves Infrared waves

Radio waves carry sound and images Microwaves heat water molecules in Infrared waves carry heat. We can see
through the air. Radios, televisions, and food and liquid, but they pass straight infrared waves with night-vision goggles
cell phones all use radio waves. The longest through glass and plastic. So when you or special cameras, both of which are
radio waves can be 100,000 times longer heat soup in a microwave oven, it’s not designed to pick up heat rather than
than the shortest ones. the microwaves that make the bowl hot, light. When you get near something hot,
it’s the hot soup inside. it’s infrared rays you feel on your skin.
76
What is white light?

Visible spectrum Now you see it...

Prisms and rainbows
Light bends when it
passes through a prism.
Each color bends at a
different angle, so they
separate out and form
a rainbow.

I can see a rainbow A well-cut diamond is the best
When it’s raining or misty, the tiny droplets of water prism there is. Because it has
in the air act like hundreds of prisms, breaking down so many different surfaces, light
sunlight into its different wavelengths. Each drop of bounces around inside, creating
water, depending on where it is, bounces a particular bright, sparkly colors.
color into your eyes. You see these colors as the bands
in a rainbow.

Visible Ultraviolet (UV) rays X-rays Gamma rays

Everything we see can Ultraviolet waves come straight from the X-ray waves pass through most Gamma rays can bore through
be seen because visible Sun. Some UV waves can burn your skin things, but not bones, teeth, or solid objects and kill living cells.
light waves bounce off and, over time, cause wrinkles and cancer. metal. When doctors want to Doctors use them in radiation
objects. Light waves That’s why it’s wise to cover up when you look at your bones, they take treatments to destroy cancer cells.
can come from the Sun go outside in summer and put sunscreen X-ray pictures to see if anything Gamma rays are also released
and from light bulbs. on your skin to block out harmful rays. is out of place or broken. when nuclear bombs explode.

77
All the colors of visible light appearing together.

Light and sound

Light and bubbles

When light hits the surface of a bubble,
it reflects off both the outside AND the
inside of its skin, producing the effect
of swirling, shimmering colors.

Bubble colors

There are different colors in a bubble
(purple, yellow, and blue) from those in
a rainbow (green, blue, and red). This
is because a rainbow splits white light
into separate colors, but a bubble
subtracts colors from light. If red is
subtracted, you see the greeny-blue
that is left behind.

Hands On These bubbles are on the surface of a soap and water solution.

Make your own Color secrets
bubble solution by mixing You can tell how thick a bubble is by the
half a cup of dishwashing colors it reflects. The blue parts of bubbles
are thickest and the black parts are
liquid with four cups thinnest. Bubbles start to turn black when
of water and four they are about to burst.
tablespoons
of glycerine.

78
What happens when you blow soap bubbles in cold weather?

Light and bubbles

Tiny planets
The patterns on a bubble
look a little like the patterns
of clouds around a planet.
Both are thin films of fluid,
so they act in a similar way.
This is why some scientists
use bubbles as model
planets—they study the
surface patterns to discover
how storms and hurricanes
develop.

The colors on the surface of A storm has been
a soap bubble appear to swirl raging on the planet
around like a storm on a planet. Jupiter for 300 years.

Bubble shapes
The water molecules in bubble solution hold tightly
onto each other, constantly pulling together. This
means that bubbles always take up the smallest
surface area possible.

When soap solution is stretched across When the solution is stretched around
a bubble wand, the smallest surface it a pocket of air, the smallest surface it
can form is a flat plane. can make is a ball.

If two bubbles meet in midair, they When three bubbles meet, they share Bursting bubbles
shrink their surface area by forming three walls. The point at which these Soap bubbles burst when they touch
a shared, flat wall between them. walls meet always measures 120 degrees. anything that’s dry (like a finger), or
when the water in them evaporates.

The water in them turns to ice—so they freeze. 79

Light and sound Fairground mirrors are
deliberately bumpy (with
Mirror,rorriM concave and convex surfaces)
to make people’s faces and
When you want to see yourself,
you look in a mirror. Mirrors bodies look odd.
reflect up to 95 percent of the
light that hits them, while
ordinary glass reflects only eight
percent. How is this possible?

Working layers

When light hits a Reflective
mirror, it bounces silver layer
straight back in (atoms shown
magnified)
Backing
Glass
the direction it

came from. You

see an exact

reflection in modern

mirrors because they’re

made from glass that has several layers

of metal and chemicals applied to the

back. These give the mirror strength Convex
mirror
and stability, and make sure it offers

a clear reflection.

Silver service Concave Taking a curve
One of the best materials for Convex Curved mirrors give weird
creating reflections is silver. The reflections and make you
Magnified silver crystals crystals that form it have flat
faces, so each one acts like a look very fat or thin.
80 tiny mirror when light hits it. Concave mirrors dip in—
Polished silver, like many other
metals, reflects light well and they make things look
gives a sharp image. On its own, larger but you see a
though, silver tarnishes in air,
so to make mirrors, it’s applied smaller area reflected.
directly to glass, then other Convex mirrors bulge out—
layers are added on the back.
they make things look
smaller, but you see more.

When was the silvered-glass mirror invented?

Ancient images Mirror, mirror
Thousands of years ago, the
The world of mirrors
only way people could see
themselves was by looking Even when you can’t see them,
into still water. In the middle there are mirrors everywhere!
ages, mirrors were made from
polished stone, silver, bronze, Light-enhancing mirrors hung
or copper. These were very in wealthy homes for thousands
dark and the metals tarnished of years. Before electricity was
(got dull and discoloured), so invented, they reflected candlelight.
they produced unclear images.
Magnifying mirrors have a small,
weird or what? concave surface. They’re designed
to help in applying makeup or
We all go through examining facial skin.
life without ever really
seeing our own face—we Dental mirrors help the dentist see
all the hidden places inside your
can only ever see a mouth. They’re small, with a handle.
reflection of it.
Rear-view mirrors are often convex
to show a larger area. They’re
attached to bicycles, cars, and trucks
so drivers can see behind them.

Car headlights and flashlights
both have mirrors behind their
bulbs to make their beams stronger
and straighter.

Sunglasses sometimes have one-way
mirror lenses. These are slightly see-
through, so you can see the world,

but other people just see mirrors.

Reflector telescopes have mirrors
set inside them to help gather and
focus light.

Mirror

Hide and seek Military uses
Periscopes use
mirrors to bend light Complex periscopes
so that people can
see around corners. in submarines allow
A simple periscope Light the crew to see the
is a tube with
angled mirrors set ocean’s surface when
parallel to each
other at each end. Mirror they’re underneath

it. Periscopes are also

used in tanks and

Spectators use mini periscopes gun turrets.

to watch a golf tournament.

It was invented in 1835, in Germany, by a chemist named Justus von Leibig. 81

Light and sound

Lenses

Lenses are used to bend light to
form an image. You have a lens
in each eye, while telescopes and
microscopes uses lenses to help us
see things that are either too far
away or too small to be visible.

What is a lens?

A lens is a transparent object that allows
light to pass through it. Lenses can be
curved on one or both sides. Lenses that
curve inward are called concave. Lenses
that curve outward are called convex.

Focal Rays of light Convex lenses bend
point Rays of light rays of light together
and bring them to
Convex lens a point called the
focus, or focal point.
The lens in your eye
is convex.

Concave lenses
spread the rays
of light apart.

Concave lens

82
How large is the biggest glass telescope lens?

How do your eyes work? Hands On Lenses
When you look at an object, Looking for lenses
the light from it travels in Make a simple
straight lines to the lens of water lens. Put a piece of You’ll find lenses in all
your eye. The lens focuses clear plastic over a magazine kinds of objects:
the light upside down onto page and drip water onto it.
the retina at the back of Now look at the letters Magnifying glasses are
your eye. Cells in the retina simple convex lenses that
turn the image into an through the “lens.” make things look bigger.
Do they look bigger?
Telescopes contain lenses
electrical message. This travels that allow us to see things
that are very far away.
to your brain, which turns the
Microscopes make things
picture the right way up. What you see that are too small for our
eyes to see look bigger.
Eye

Brain Lens (lies
behind iris)

Electrical Upside-down Retina Video projectors magnify
message images so they can be
image (back of eye) displayed on a screen.

That’s better! Some cameras have a
If someone is near-sighted, distant objects look blurred. number of lenses to
This is because the lens focuses light in front of the produce different effects.
retina instead of on it. If far-sighted, nearby objects are
blurred, and light focuses behind the retina. Glasses or Pupil shrinks in
contact lenses help the eye focus light in the right place. bright light.

Near-sightedness Far-sightedness Bright light Iris Muscles around
iris contract.
Before Light focuses in Before Light focuses Pupil expands
front of retina. behind the retina. in dim light.

Dim light Muscles
around
Instant reaction iris relax.

Lens There are muscles in the eye that
Near-sighted people can focus on things up
close but not in the distance. Concave lenses Far-sighted people can focus on things in the help the lens change shape so
lengthen the light’s path through the eye. distance but not on close objects. Convex you can change focus quickly to
lenses help shorten the light’s path. look at things that are near or
After far away. Other muscles around
After
A concave lens spreads the
light out before it hits the eye. the iris control how much light

enters the eye. Your pupils get

bigger to allow more light in and

A convex lens bends the rays help you see in dim conditions.

together in front of the eye. 83

The 40 in (1 m) lens in the Yerkes telescope in Chicago.

Light and sound This is an
X-ray of
How light works an energy-
efficient
For thousands of years, the only light we bulb.
had was from oil lamps, candles, and gas
lamps. Then electricity was invented and Wires inside
we had lights we could switch on and off! the fixture
carry electricity
to electrodes.

Basic bulbs Energy-saving light bulbs don’t Transformer
have a filament. Instead, they boosts
Traditional light use electrodes to release tiny electricity to
bulbs contain a small particles called electrons. increase
coil, or filament, made These energize the gases inside brightness.
from tungsten, a strong the tube and make them glow.
metal that can get incredibly The light produced inside these Tungsten
hot without melting. When an bulbs is actually invisible, but electrodes
electric current passes though a special coating on the bulb release
turns it into visible light. These electrons
lights are much cooler than from electric
traditional bulbs, last longer, current.
and use less energy.

the tungsten coil it gets so hot Glass tube
that it glows, and it’s this glow contains
that provides us with light. argon and
mercury
LED bulb gases.

LEDs can be used Small and bright
for signs and Very tiny light bulbs called LEDs
outdoor display (light-emitting diodes) are used in
screens. They all kinds of electronic equipment,
give off a very such as stereos, computers, and
bright light and Christmas lights. They produce
come in lots of light by passing electricity through
different colors.

a special material that gives off

Lead connecting light of one particular color.
to electricity
supply.

84
How many bulbs are used to light the Empire State Building in New York City?

Cyan Mixing colors How light works
Visible light looks white to us, but if you
White light is direct it through a prism it splits into weird or what?
a mixture of Magenta different colors. You can reverse this
all colors. Every1/8 in2 (1 cm2)
process to turn different colored light of the Sun’s surface
back into white light. When you mix emits as much light as
red, green, and blue you get white. a 15,000 watt bulb!
Mix any two and you get magenta
pink, yellow, or cyan blue.

Lasers

Lasers are devices that emit thin, powerful
light beams. The light waves in a laser are all
the same wavelength and line up exactly.
This makes laser beams so intense they can
cut through metal. Lasers are used in surgery,
CD players, surveying, and industry.

Lasers are used to treat eye problems such Laser surgery Lasers can be used in light
as near-sightedness. Lasers are used for shows and displays.
many types of surgery.
The heat of the light is
used to burn through
tissue without cutting
it with a scalpel.
Lasers are also used to
shatter kidney stones,
and shape cavities for
fillings in dentistry.

There are 3,194,547 bulbs. 85

Light and sound 3, 2, 1, liftoff!

Fireworks Light the fuse and stand
back! The flame travels up
Bursts of color and noise fill into the firework, where
the sky—fireworks are packets it quickly sets fire to
of chemicals that explode gunpowder inside.
when lit. A fuse ensures the
explosion is delayed. 6. Explosion!

Early fireworks had The chemicals inside
bamboo casings the firework explode,
packed with releasing their energy
chemicals. as light, heat, and
sound. Bang!

The arrows were 5. Stars
shot into the air.
The gunpowder is mixed with
First fireworks stars—chemical mixtures that
It’s thought that the first fireworks were used make a firework’s flashes of color.
in China more than 2,000 years ago. They were
made from bamboo and used in religious 4. Gun powder
ceremonies and to celebrate New Year.
Explosive gunpowder is stored in
a chamber inside the firework.

3. Propellant

Inside the cardboard case,

gunpowder burns quickly to

shoot the rocket skyward.

Hi-tech displays 2. Fuse
Firework displays are often run by computers.
The computer sends an electric spark down a Fuse paper contains chemicals that

burn steadily, allowing time for a

person to stand back after lighting.

wire to light each fuse. It makes fireworks 1. Launch tube
launch in the right order and explode at
In big displays, fireworks
their highest points in the sky.
are put inside metal tubes.

These stay on the ground.

86
What is the firework called the Catherine Wheel named after?

Fireworks

Rainbow of color

Fireworks contain
metallic salts—these
make fireworks explode
in different colors.

Firework patterns Purple is made from
When fireworks explode, they create different patterns
in the sky. Here are six to look out for next time you go Sr Cu stronium salts
to a firework display. and copper.

Red comes from
lithium salts.

Li

Ring shell—a bright, Palm trees—stars move Crysanthemum—a Orange flashes
expanding ring of stars. up as a “trunk,” then pattern that leaves long are created by
spread out as “branches.” trails of stars.
Ca calcium salts.

Yellow color comes
from sodium

Na compounds.

Green lights are made
using barium

Ba compounds.

Serpentine—many stars Fish—a swarm of stars Willow—in this, star trails Blue flashes come
that zigzag outward as they moving randomly across fall nearly all the way to from copper
fall. the sky. the ground.
Cu compounds.

An instrument of torture! 87

Light and sound Sound waves
Sound waves spread
Measuring sound out in all directions
from where they are
All the sounds we hear are made up of made. As a wave
waves that travel through the air to our moves through the air,
ears. We can record the waves to see the air molecules are
their shapes. Different sounds make squeezed together and
different-shaped waves. then stretched apart.

What is sound?

Sound is made up of waves of vibrations moving
through the air. Any object that vibrates (moves

quickly back and forth) can make a sound,
just like this drum.

Hitting with a drum stick Sound wave
makes the drum skin vibrate.
s
drum is a source of sound.The skin of a drum is
A stretched very tight.

When you hit a drum its skin Hands On
vibrates up and down. Sometimes
you can even see the skin moving. Hold one end
As the skin vibrates, it pushes and of an rubber band on the
pulls on the air around it, making edge of a table. Stretch out the
the air vibrate, too. other end and then pluck the
band. Can you see vibrations

and hear the sound
they make?

88
Can you hear sound in outer space?

We can pick up sound with a Microphone Flatter sound waves Measuring sound
microphone. Inside is a thin metal have a small amplitude.
plate that vibrates when a sound They sound quiet. Decibel levels
wave hits it. The microphone
turns the pattern of the Crest (top of wave) Loudness is measured
vibrations into an in units called decibels.
electrical signal. Here are some examples.

Leaves rustling

30 dB

Taller waves have Quiet music
a large amplitude.
They are loud sounds. 50 dB

Oscilloscope Speaking

Trough “ 60 dB

What sound looks like (bottom Vacuum cleaner
of wave)
70 dB
Sound waves can be shown on a
Busy traffic
machine called an oscilloscope. The
80 dB
height of a wave is called its amplitude.

The crests show where air is squeezed and

the troughs show where air is stretched.

Slower than light Baby crying 85 dB
Sound waves travel more
slowly than light. You can tell 85 dB
this during a thunderstorm.
First you see the lightning, then Pneumatic drill
you hear the thunder, perhaps
several seconds later. Yet they 125 dB
happen at the same time.
Jet engine Listening to
A loud, explosive storm sounds of
140 dB 85 dB and
above for a
Frequency and pitch long time
can damage
your ears.

Frequency is the number Sonic boom!
of crests on a sound wave Sound waves travel through air
that pass by each second. at about 750 mph (1,200 km/h). When
High-frequency sounds,
such as bird song, sound a plane travels faster
high-pitched. Sounds with than the speed of sound, it
low frequency, like creates sonic boom—a
thunder, are low-pitched. “shock wave” that makes a
very loud noise.

High-frequency sound waves

89
No. There’s no sound because there’s no air for sound waves to travel through.

Light and sound

How ears hear

Sound travels in waves. When these

waves reach your ears, they’re The outer e
carried to your brain, which tells

you what sound you’re hearing— ar contains the earThe stirrup bone in
your middle ear is
your mom’s voice, for the smallest bone

in your body.

example, or the pop of Outer ear
a bursting balloon.

Ear, ear, ear

Your ears have three parts—the outer

ear is the part you see. Your eardrum, canal.

which separates the outer ear from the

middle ear, picks up sound vibration Sound waves This tunnel is called
and passes it onto the three tiny bones of the ear canal.

the middle ear. The inner ear contains

bone, liquid, and tiny hairs.

Headphones let weird or what? The part of your ears
you hear one sound while that’s on the outside of
blocking out others. People often suffer
hearing loss (deafness) when your head helps to
they get old. But if you listen “catch” sound waves.
to very loud music all the time, The strange folds in your
or sit too near the speakers at ears help you work out
rock concerts, your hearing when sounds are behind

could be damaged or above you.
forever.
Better than one
The fact that sounds Ears are really very
reach one ear before the
other helps your brain to smart—they don’t
work out where they are. just identify sounds,
they can also tell how
90
Are there any sounds we can’t hear? far away they are,
and which direction
they’re coming from.

How ears hear

All change

When sound enters your

ears, it vibrates inside. The

vibration is picked up by hello Echoes happen when
liquid in the inner ear, which hello sound waves bounce
vibrates slightly, causing tiny off one surface onto
hairs to move. Cells at the another, and another,
base of these hairs transform and another, getting
the vibration into electrical weaker every time
they hit your ears.

impulses that travel along In an echo-free chamber, all the Repeating sound
nerve pathways to your brain. surfaces are lined with fiberglass

wedges that absorb sound. Sometimes you hear a sound

once, then over and over again,

getting fainter every time. This

Middle is called an echo. You can hear
ear echoes in small spaces with
hard walls, like wells, or where
Inner ear

there are lots of hard surfaces

all around—in a canyon, cave,

The cochlea is a fluid- or mountain range.
filled, shell-shaped hollow
bone in the inner ear that

Ear drum senses sound vibration. Helping ear

Hearing can get damaged or

This tube leads from your ear to Eustachian worn out. If any sound gets
the back of your nose and throat. tube through, a hearing aid will
make it louder. Cochlear

Whispering walls implants do even more—
they stimulate nerves in the

Sometimes, a hard, curved, surface causes sound to behave in cochlea, so they can help

strange ways. Visitors to the dam at the Barossa Reservoir in those who are

South Australia can whisper at one end, and someone at the totally deaf.
other end—over 460 ft (140 m) away—can hear them clearly.

This is because the curve causes the sound waves to bounce in

a series of jumps that run all along the length of the wall.

Cochlear implants are
suitable for children.

OVER 460 FT (140 M)

Yes, dogs, snakes, and bats can all hear higher-frequency sounds than humans can. 91

Light and sound Pick

Electric guitar You can pluck the
strings with your
When you pluck the strings fingers or a pick.
of a traditional (acoustic)
guitar, the sound is Frets show the
magnified in the guitar’s musician where to
hollow body. An electric place her fingers to
guitar’s body is solid, change the note.
but it still makes a
very LOUD NOISE! Six or twelve
metal strings
1 Pluck the strings are each tuned
to a different note.
Play an electric guitar
when it’s turned off. The neck carries the
The strings vibrate, fingerboard and
but the sound they supports the strings.
make is as quiet as
a whisper. The solid body is
made from a single
The pickup detects the piece of wood.
vibrations of the strings.
3 Amplified
The bridge has a
saddle that lifts the The electrical signal
strings clear of the pickups travels from the
so they can vibrate easily. pickup along a wire
to the amplifier. The
An amplifier amplifier strengthens
boosts the the signal, and a built-
electrical in loudspeaker blasts
signals to out the sound.
make the
sound loud.

92

Electric guitar

2 What picks up the sound? A pickup up clos
e.
When you turn on the guitar, the pickups start MAGNETIC FIELD
working. Pickups are made of wire wrapped

around a magnet. The magnet has a Guitar Magnet in
magnetic field around it. When strings string pickup

vibrate they change the pattern of the

magnetic field, sending currents through

the coil to the amplifier. Signals travel
to amplifier

Machine heads are like Volume and
screws and can be twisted tone control knobs
to tighten or loosen the
string for tuning. Coil of wire
MAGNETIC FIELD

Pickups convert
vibrations from
the strings into
electrical signals.

Electric current The electrical
signal from the pickups travels
through wires to the controls,
then onward to the amplifier.

Coil of wire in pickup

weird or what? Different electric guitars

The electric guitar was Guitars come in all sorts of shapes and sizes. The
first championed by jazz shape of an electric guitar does not affect its sound.
musicians. They loved the
way this loud instrument Semi-acoustic guitars are a Double-headed guitars
let them be heard above mix of electric and acoustic, let musicians switch sounds
with hollow bodies. without switching guitars.
the noise of a
brass band. Bass guitars only have four Custom guitars are
strings and play the lower whatever shape or size
notes in a piece of music. a musician prefers.

93

Bits and bytes

Bits and bytes Bit
A bit is a binary digit and
Digital technology relies on the silicon can be either a 0 or a 1.
chip and the binary code. Data that is Each bit can hold the
sent to and from digital appliances is answer to one simple
sent in binary digits called bits. It is question, using 0 for “No”
measured and stored in bytes. and 1 for “Yes.”

Silicon chips and computers Byte
A byte is made up of 8 bits
Personal computers were made possible by using and is the measurement
silicon to make microchips. Silicon was chosen since unit used to describe the
it’s a good semiconductor—it can keep the flow of storage capacity and
transfer rate of digital
electricity going or make it stop. systems.

Sand covers ov 1 kilobyte is 1,024 bytes
1 megabyte is 1,024 kilobytes
Shallow 1 gigabyte is 1,024 megabytes
mantle 1 terabyte is 1,024 gigabytes
1 petabyte is 1,024 terabytes
1 exabyte is 1,024 petabytes

Ever heard of silicon?
Silicon and oxygen make
sand—and there is a LOT
of sand in the world!

Lower mantle er half the Earth’s surface. Lump of silicon

Outer core
(molten)

Inner core Crust and
(solid) lithosphere

94 How many transistors can fit on a single silicon chip?

What’s inside? Bits and bytes

A silicon chip contains Curiosity quiz

millions of transistors (things Look through the
“Bits and bytes” pages
that control the flow of an and see if you can identify
the picture clues below.
electric current) and other

tiny electronic parts that are

all connected to each other.

A silicon chip can be very small—
less than 1⁄10 square in (1 cm2) and

about 1⁄10 inch (1⁄2 a mm) thick.

Silicon wafer

How is a silicon
chip made?
Electronic circuit patterns
are photographed onto disks
of silicon, called wafers.
Chemicals are used to etch
the patterns into the silicon
in several layers. The wiring
that connects up the circuit
is made in the same way.

Pattern to be etched on chip.

Individual chips
Wafers are tested to make
sure they work. After being
checked they are cut into
individual chips, which are
placed into protective cases.

Individual chip from wafer Hundreds of chips can be Become
Finished chip in package. made on a single wafer. an expert...

on binary code,
pages 98–99

on the Internet,
pages 110–111

Some silicon chips contain two billion transistors. 95

Bits and bytes Address Book
Business
Inside a laptop Calculator

We use computers to do all kinds of Calendar
things—play games, watch videos, Dictionary
and surf the Internet. All these things ASPN
are controlled by a microprocessor
that acts like a tiny
electronic brain.

Laptop computer The microprocessor, or central
processing unit (CPU), is the single
All the components of a most important chip in a computer.
personal computer can be This electronic circuit is what makes
built into a convenient folding all the programs run. It is hidden
package the size of a book. inside the computer.
Some laptops use wireless
technology to interact with
printers, scanners, and other
devices by radio waves.

The hard drive is where all
the computer’s programs and
data are stored permanently.
Most laptops can store up to
100 gigabytes of data.

Instead of a mouse, a trackpad is used to DVDs or CDs
control the cursor on screen. By dragging can be played
a finger over the trackpad and clicking or copied on
buttons it is easy to scroll vertically and this drive.
horizontally, or open and close windows.

96
What is a netbook?

English Inside a laptop
Area
weird or what?
Japanese
Engineers have designed
Results portable computers that can

INDU be worn on the body and
AAPL controlled using blinks
of the eye.
Sign post
Laptop and
Quick search computer screens
use hundreds of
tiny red, green, and
blue liquid crystal
cells to produce an
image, just like
a television.

Picture search Computer talk

Memory holds data that
the CPU needs to read and
write quickly.

Hard drive saves files
and programs when the
computer is switched off.

Ports provide connections Mobile broadband
to external devices. An dongle connects laptops
MP3 player, digital to the Internet wirelessly.
camera, or external hard
drive can be plugged into Bytes—all data on a
various ports. You can
also transfer your photos 1MB computer is held in units
and videos using a
memory card slot. called bytes.

A light sensor activates Cables connect the laptop
the illuminated keyboard to input devices, printers,
in low-light conditions. and the Internet.

Input devices include
computer mice, joysticks,
and drawing tablets.

97
It’s a small, lightweight laptop designed for Internet access on the move.

Bits and bytes

Binary code

The binary code is made up of
two digits: one and zero. The code
converts images, text, and sounds
into numbers in order to send
information from one digital device,
such as a computer, to another.

Binary numbering
Computers use binary
numbers because they
are easier to handle. In
binary, the digits (read
from the right) are worth
1, 2, 4, 8, and so on—not
units, tens, and hundreds.
In ordinary numbers,
“1,001” is one unit, no
tens, no hundreds, and
one thousand. But in
binary “1001” is one 1,
no 2, no 4, and one 8,
which equals 9.

How a motherboard works 2. I/O controller
make the central
The motherboard is the main processing unit
circuit board in a computer. (CPU) pause.
It connects all the main parts
and passes on instructions.

CPU

1. Keyboard communicates I/O Controller
with motherboard via input/ Motherboard
output (I/O) controller.

98
How many ones and zeros can a fiber-optic cable carry per second?

Hands on Binary code

Using the code Sending numbers
below you can write out your Fiber-optic cables are used to
transport binary numbers from one
name in binary code. Use computer to another. An electric
uppercase letters for the current carries the numbers as a
beginning letter of your first stream of digital data. A laser turns
and last name and lowercase the current into pulses of light that
for the remaining letters. are sent through the fiber-optic cable.

A cable used for telecommunications has
100 or more optical cables inside.

ASCII Code: character to binary code

0 0011 0000 F 0100 0110 U 0101 0101 The first
signal is sent
1 0011 0001 G 0100 0111 V 0101 0110 down the
2 0011 0010 H 0100 1000 W 0101 0111 middle.

3 0011 0011 I 0100 1001 X 0101 1000 A central steel A second signal travels
cable protects in a zigzag line.
4 0011 0100 J 0100 1010 Y 0101 1001 the fibers.
A third signal
5 0011 0101 K 0100 1011 Z 0101 1010 A polymer outer travels by
sheath keeps the fiber reflection but
6 0011 0110 L 0100 1100 For lower case safe from damage. doesn’t get in
7 0011 0111 M 0100 1101 letters, a–o start the way of
8 0011 1000 N 0100 1110 with 0110, while The center is made other signals.
9 0011 1001 O 0100 1111 p–z start with from glass or plastic.
A 0100 0001 P 0101 0000 0111. The next
B 0100 0010 Q 0101 0001 four digits are Light is reflected back
C 0100 0011 R 0101 0010 the same as for into the core by glass
D 0100 0100 S 0101 0011 upper case, so or plastic cladding.
E 0100 0101 T 0101 0100 a = 0110 0001.

3. Central processing unit (CPU) stops what
it is doing and accesses memory (RAM) to run
the keyboard driver built into the program.

RAM

5. CPU tells the graphics 6. Monitor displays
processing unit (GPU) to characters on screen
put that character on
the screen.

4. Keyboard driver finds out Graphics processing unit
what key was pressed and
what character this represents.

100 billion ones and zeros per second at almost the speed of light. 99