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COMPUTERSTO

RE AND PROCESS INFORMATION

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SATELLITECOMMUNICATION

Copyright © 2010 Top That! Publishing plcTide Mill Way, Woodbridge, Suffolk, IP12 1AP, UK

www.topthatpublishing.comTop That! is a trademark of Top That! Publishing plc

All rights reserved

Inventions

Washing MachinePages 4–6

IronPages 7–9

MicrowavePages 10–12

AirbagPages 13–15

Sewing MachinePages 16–18

ToasterPages 19–21

RefrigeratorPages 22–23

Petrol EnginePages 24–26

Steam EnginePages 27–29

Jet EnginePages 30–31

GearboxPages 32–34

CONTENTS

2

ComputerPages 35–37

Digital VersatileDiscsPages 38–39

TelevisionPages 40–41

TelephonePages 49–51

X-Ray MachinePages 57–59

MicrophonePages 60–61

RadioPages 44–45

CONTENTSSatellitesPages 42–43

Light BulbPages 52–53

CameraPages 54–56

CalculatorPages 46–48

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It’s pretty simple to operate a modern washing machine; just place yourclothes in the front, add soap powder into the little drawer, make sure thesetting isn’t too hot (or it will shrink your favourite jumper), and press the‘on’ switch. What goes on inside the machine, however, is quite amazing.

WASHING MACHINE

In most modern machines all you can see insideis a big metal cylinder, which is where the washinggoes. In some older machines there will be a twistedplastic pole that moves the clothes around to makesure they get really clean. Look at the pictures to seethe main parts that make the machine work.

What’s inside a washing machine

Outer cylinder – this is attached to thebody of the washing machine, andmounted to let the inner cylinder shakeinside without bashing into any otherparts. It also seals in the water.

Inner cylinder– clothesare heldinside here

Motor – an electronically powered motorturns a spindle,which is attachedto a belt that turnsthe cylinder around

5

Pump – thismoves water inand out of theouter cylinderas needed

Concreteblock forstabilising

Valves – the two valves feed intothe one pipe. If the highesttemperature setting is selected, thenthe ‘hot’ valve opens. If a cool settingis chosen, then the ‘cold’ one opensinstead. If you need warm water,then they both open simultaneously

Pipe – takes away all thewater from the cylindersand discharges it safely

6

When you spin a container of liquid around really fast,the liquid moves to the sides of the container. Try it(outside) with a bucket about a third full of water. Spinit around repeatedly with your arm outstretched – ifyou do this fast enough, the water won’t spill outbecause it is ‘clinging’ to the sides of the bucket. Whenthe inner and outer cylinders of a washing machinespin, the water moves to the edge and is removed bypipes, which makes your clothes a little drier.

Soaking clothes in warm, soapy water makes the dirtdissolve and float off the material. Swooshing themaround at the same time speeds up the process andalso helps to move the dirt away from the clothes.Changing the dirty water for clean water carries offthe dissolved dirt and gives any remaining dirt anotherchance to be cleaned off the clothes.

How do clothes get clean

What’s the spin cycle

Soaking dissolves the dirt

Rotating action lifts dirt from clothes

Clean water flushes dirt away

The average washing machine has a capacity(holds when full) of around 5.5 kg (12 lb) of clothes.That’s around 55 pairs of socks!

The reason washing machines are so heavy is thata large block of concrete needs to be attached fromthe main frame to counterbalance the force of thewashing being moved around and around, especiallywhen the machine is spinning the clothes.

FACT BYTES

7

Without the modern iron, ironing our clothes would be a long, messy andeven dangerous process! Before the introduction of electricity, heavy lumpsof metal, heated by the fire, were run over clean clothes, but they oftenleft behind a line of dirt in the process.

IRON

The first electric iron is credited to Henry W. Seely ofNew York in 1882. In the same year, a Frenchcompany created an iron that was heated by an arc(semicircle) made of carbon, but this was highlydangerous, and in 1892, both Crompton and Co. andthe General Electric Company managed to create arelatively safe electric model. It set an industrystandard for many years, being made from only fourmetal components, and a wooden handle and someelectronic parts.

Who invented the electric iron

A housemaid uses an electric iron on a lace doilyin this advertisement from General Electric

Steam combined with the heat and weight of the ironhelps to stretch out the molecules in your clothes,smoothing away any creases – but you don’t want wetclothes! That’s why the water to make the steam ispassed through tiny holes in the hot base of the iron –it turns into steam before it gets the chance to makeyour clothes soaking wet again.

Why does steamhelp ironing

By 1939, the electric iron had become the second-mostpopular household appliance (number one was the radio).

Some weird and wacky irons have been invented since1882 – one model had cords that plugged into electric ironing boards! The travel iron, friend of the business travellerand holidaymaker alike, is a particularly lightweight versionthat can run on a 120-volt power supply.

FACT BYTES

8

The main part of an iron is the heating element, likethat in an electric oven, which makes it hot. An ironalso needs a metal base, a thermostat (to stop the ironoverheating and burning your clothes) and a controlbutton to set it to the right temperature.

What’s inside an iron

Metals expand at different temperatures, so two stripsof metal, made from different types, are fixed together. The strip that expands more forces the other strip tobend. When the iron goes above the temperaturesetting you want, this metal strip bends so much that itmoves, breaking the electrical circuit. The flow ofelectricity stops so the iron cools down.

How does the thermostat work

Hot plate – this is coatedin a special alloy (mix) ofmetals, which helps toprevent the metal sticking to clothes. It alsohelps the iron to glideover clothes as smoothlyas possible

Water tank – fill a littleplastic jug with waterand pour it into the holeat the front of the iron. The water will run downa tube and fill up thetank. The water is heatedto create steam

Element –causes thebase of theiron to heat up

Thermostat – a heat sensitive strip cuts thepower supply as soon asthe chosen temperatureis reached, and the current returns when theiron has cooled down

Control button –you can set this tothe temperaturemost suitable forthe fabric that youwant to iron

9

Electricity is passed through a horseshoe-shapedpiece in the base of the iron (the element), which getsvery hot. This heat is also conducted through themetal base to the whole of the bottom part, which

then smoothes your clothes. The top of the iron,including the handle, is made of non-conductivematerials like plastic, so you can hold the iron safely.

Resistor

Thermostat

Screwto adjust thermostat

Plasticouter casing

Steam/spray nozzle

Tube for water

Steambutton

Spring support

Level indicator

Steam mechanism

Base

Handle

Cable

Water tank

Temperature indicator

How does an electric iron work

Element

10

Microwaves have come a long way since the wartime discovery that theycould be used to heat up food safely. You can heat up yesterday’s spaghetti,boil potatoes, have dinner ready in five minutes – simply by programming thecontrols. Ping! Grub’s up!

When were microwaves invented

The heating effect of microwave ovens was accidentlydiscovered by American Percy Spencer in 1945.Microwaves were much bigger than they are nowadays– about the size of a fridge! Since then, they havespread from restaurant and canteen kitchens into thehomes of most people in the Western world.

MICROWAVE

Why can’t I put metalobjects inside

The energy produced by microwaves causes watermolecules in food to rub together, which makes foodhot. Metal doesn’t contain water so there is nowherefor the energy to go. Sparks fly from metal objectsplaced inside a microwave and break the magnetron– so never leave your fork inside!

The main parts of a microwave are the power source,the magnetron, the controls, the stirrer blade, theturntable and the metal walls. The power goes to themagnetron, which is the important part that creates themicrowaves. These are moved around the oven by thestirrer blade, and reflected off the metal walls so thatthey hit the food from all angles. The controls set thecooking level and the time you want to cook for. Theturntable moves the food around so that it cooks evenlythroughout.

What’s inside a microwave

Outer casing

Magnetron tube –this tube uses electricaland magnetic currentsto produce a non-stop

flow of electromagnetic energy

Stirrer blade

Cooling fan

High voltagetransformer

Timer and controller – choose yourdesired heat and time setting, and

electronic circuits do the rest

Screen

Turntable

Inner casing

Power cord

Fuse holder

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How do microwavescook food

When microwaves are beamed around a sealed container (the microwave oven) they make themolecules found in food and liquids rub together,which creates heat. This allows the food to be heatedfrom many different angles, making it cook evenly.

Why does food cook inside out

In reality, it doesn’t cook inside out – it cooks the sameall the way through. However, that’s different from anormal cooker, where the food starts to cook on theoutside first. In a conventional oven, the heat cooks theouter layers of the food and then works its way to theinside through radiation. The waves in a microwaveoven go right through the food and heat it up muchmore evenly. Nowadays, some microwaves incorporatea grill or conventienal oven, so food can be cookedquickly but still be browned.

Microwaves are absorbed by whatever’s inside,and the molecules in the food transform the

waves into heat

Until Percy Spencer invented the microwave oven, the mainuse for a magnetron was to help Britain spy on German warplanes! It was almost by accident that scientists foundmicrowaves could be used to cook food - infact, it was saidthat a chocolate bar melted in Percy Spencer’s pocket whenhe was testing a magnetron in a radar. Spencer directed themagnetron’s energy into a metal box and microwaved thefirst popcorn!

FACT BYTES

Microwaves heat food evenly, but are unable tobrown or bake food like regular ovens

13

Airbags are a relatively recent, but very important, invention. Previously,there were only seat belts to protect people in a car crash, but the last twentyyears has seen most cars fitted with airbags as standard.

How do airbags work

AIRBAG

If a car crashes, a sensor detects the sudden stop andsets off the working parts of the airbag inside. Thereare two working parts – an ignitor and a solid propellant. The ignitor lights the propellant to cause achemical reaction, which gives off nitrogen gas. Thisgas inflates the bag, but quickly leaks out through tinyholes so that the bag gets smaller again and the passengers aren’t trapped.

Airbags are put under many intense tests usingdummy crash victims before they are used in a car

What are the bags made ofand what’s inside them

The bags are made from a thin fabric, usually nylon,that can be folded into a small space. The bags fill assodium azide reacts with potassium nitrate to producenitrogen gas.

This cutaway of a steering wheel shows theairbag, tucked in (white)

14

In the blink of an eye theignitor lights the propellantand the airbag fills with gas,which quickly escapes throughtiny holes in the bag so thatthe person can breathe

Way back in WWII,a patent was given fora soft inflatable crash-landing pillow to befitted in aeroplanes.

The sensors receivea message from a‘speed gauge’ knownas an accelerometer.

FACT BYTES

You cannot see the bagbefore inflation as it isfolded into the steeringwheel, the dashboard,the seat or the door

When there is acollision force equal tohitting a brick wall at16–24 kph (10–15mph), a sensor tells thebag to inflate

15

Although it’s better to be thrown forward or sidewaysinto a cushion of gas than into the hard parts of a car,airbags themselves can sometimes cause injuries, so itis possible to turn some airbags off. If an adult issitting too close to the airbag when it goes off (lessthan 25 cm/10 in. away), or it goes off in their faceinstead of their body, it could seriously harmthem. With children, it’s even moreimportant that the airbags don’texplode into them. Babiesand toddlers in car seatsshould only be fastenedinto the front seat of a carif the airbag has beenturned off.

The bag pops out from its storage space in one twenty-fifth of a second! It travels at up to 320 kph (200 mph).That’s super fast! The airbag has only a fraction of asecond to act to give the driver or passenger the bestpossible protection.

Airbag 320 kph (200 mph)

Car 160 kph (100 mph)

Bullet 3,218 kph (2,000 mph)

Jet Fighter 2,333 kph (1450 mph)

Can you turn an airbag off

Airbags can save lives.In modern cars they

are placed in the sidesas well as the front.

How quickly does it all happen

16

You might not have much interest in a sewing machine – boring, huh? Withoutit, however, you wouldn’t be able to wear your favourite jeans or hoody, andwe might all still be wearing smocks like they did hundreds of years ago …

Who invented the sewing machine

One of the earliest successful models, used mostly forsewing French army uniforms, was patentedin the 1830s by Barthélemy Thimonnier. He opened afactory with around eighty sewing machines, but itwas destroyed by Parisian tailors, who thought hisinvention would ruin their business. One of sewing’sfamous names, Singer, was a businessman whosuccessfully manufactured and marketed sewingmachines, but he cannot claim to have invented them.

SEWING MACHINE

What is a ‘feed dog’

This is the part of the machine that keeps the materialmoving as you sew. It is next to the point of the needle, and looks like rows of sharp metal teeth. After each stitch, it ‘feeds’ more material through themachine so that the stitches form a long row (and don’tfall on top of each other). You can change the lengthof the stitches by altering the amount of material thefeed dog moves through during each stitch.

A Singer sewing machine A feed dog keeps material moving

Feed dog – this is linked toa rod on the lower driveshaft, which moves it forwards and backwards,‘feeding’ the fabric throughrows of metal teeth andkeeping the tension constant

Motor – anelectrical currentturns the drivewheel with the useof the drive belt.The motor iscontrolled by a footpedal, so that theuser can decide onthe speed

Crankshaft

Drive belt –moves atexactly thesame speed as the drivewheel andkeeps all ofthe partsmovingsmoothly

Bobbin case – this small,circular case contains a spoolonto which a secondary cottonis wound

Needle – thespool of cottonthat runs fromthe top of themachine is fedthrough hereand moves upand down

Drive wheel – this turnsthe upper drive shaft. Theend of the shaft connectsto a crank, which movesthe needle up and down

The primary cottonreel is placed ona spindle

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How is a stitch achieved

If you sew by hand, you push a single needle andthread all the way through the material, pull the threadtight, and then push it back in the opposite direction tocomplete one stitch. Sewing machines are cleverbecause they can make a tight, secure stitch withoutpushing the needle all the way through the material.Instead, they separate two pieces of thread which arelooped together.

What makes up a sewing machine

Apart from the electrics, a sewing machine needs onlya few things to make it work: thread, needle, feed dogand bobbin hidden underneath the needle. When youpress the foot pedal, the electrics drive a series of beltsand wheels, which make the material, needle andbobbin move to create the stitches.

To create asimple chainstitch, the threadruns through the needle from thecotton reel

A stronger type ofstitch is the lockstitch. A loop ofthread is carriedall the way aroundthe bobbin. Whenit reaches the topof the case, itis carried over thebobbin and pulledtaut by a lever,making a stitch

The needle goesthrough thematerial, forminga loop on theunderneath ofthe fabric. This iscaught by a hookand creates astitch

The Brother NX-400sewing machine hasan amazing 294in-built stitching styles,including swirls,letters, numbers andflowers, as well as thesimple running andsatin stitches.

FACT BYTES

A presser foot helps tokeep the fabric niceand flat beneath theneedle. Presser feetcome in differentshapes, making it easyto stitch anything, froma button hole to a zip!

FACT BYTES

Even the Romans were partial to a piece of toast. The word ‘toast’ derivesfrom the Latin ‘tostum’, meaning to scorch or burn. Stale, old bread canquickly be transformed into lovely, crunchy toast with a little help from yourmodern-day toaster. Toasters have come a long way from the first machines,which only toasted one side at a time!

TOASTER

People have been using a flame to heat up their breadfor centuries. However, it is unknown as to who inventedthe first electric toaster. Various inventors introducedtheir models, but many failed due to fire hazards. In1921, the first pop-up toaster was patented whenCharles Strite created a toaster with springs and a timer.One hundred models were made, and Strite’s creationhit the headlines when it was described as an amazingnew invention that ‘makes perfect toast every time!’.

Who invented the toaster

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Over the years people haveused a variety of differenttools to create crunchy toast,ranging from a toasting fork(left) held near the fire, to thefancy metal 1930’s toaster(above)

The timer is connected to an electronic circuit which,when the toast is ready, sends a message to the breadlifter so that your toast pops out just as you like it.

Medieval recipes suggest that white toast was enjoyedby the wealthy. White bread was considered the finesttype of bread worthy of toasting – and they even cutthe crusts off, something poorer people couldn’tafford to do!

FACT BYTES

Electronic circuit –directs messagesfrom the timer dialto the lifter latch todetermine how longthe bread is helddown for

Toasting plates – thinsheets of metal onto whichthe elements are fixed

Elements –very thinpieces of metalthat heat up

Crumb tray – collects bitsthat fall off the toast

Bread lifter– receivesa signalfrom thetimer dialsvia acontrolpanel sothat itknowswhen topop up

Bread lifterlatch – pressthis down tostart thetoastingprocess

Level dial –turn this toset thelength oftime yourbread is‘in’

Outer casing

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What are the elements made of

The elements of a toaster are very thin metal wireswrapped around the toasting plates. Look carefully down into the toaster next time you use one(but don’t get too close). You’ll see thin lines glowingorange – these are the wires getting hot. Toasters usenichrome wires, made of an alloy (a special mixture)of nickel and chromium, which can get hot withoutfalling apart!

It’s nearly as easy as it looks! Your uncooked breadgoes into the slot on top of the toaster and rests on anarrow platform. When you press down the handle,the platform moves the bread down inside themachine. The handle also connects heating elements(like those in an iron) to the electricity, which starts toheat them up. The elements give off enough heat tocook the bread and turn it into toast.

How does bread turn into toast

Modern toasters produce reliable results!

FACT BYTES

Some modern toasters are able to print imagesand logos on bread slices!

When bread turns into toast, the outer layers ofproteins and carbohydrates combine to give thatcrisp, brown surface.

The elements get hot and turn bread into toast

22

Humans have long known that keeping food cold helps keep it fresh and canmake it last longer. Before the invention of the fridge, it was common to cutice in the winter and store it underground for use in warmer weather. It wasnot until the early 20th century that the first recognisable fridge wasintroduced – but it cost twice as much as a car to buy!

Why do we need refrigerators

REFRIGERATOR

Scientists discovered that keeping food cold slowsbacteria from multiplying and spreading, so reducingserious illness and even deaths from food poisoning.Simply keeping your milk in the fridge means that itwill last for one or two weeks, instead of a few hoursif it’s left out in warm temperatures.

How does a fridge work

If you look at the back of a fridge, you will see a verylong pipe. This carries a special substance calledrefrigerant. The refrigerant starts as a liquid, but whenit heats up it turns into a gas. This gas travels aroundthe pipe until it gets to a condenser, which turns itback into a liquid again. The basic idea is that theheat used to turn it into a gas comes from the foodinside the fridge. Each time the refrigerant travelsaround the pipe it takes a little more heat from thefood, cooling it down.

Once heated,refrigerant moleculesturn into gas andmove around freely

When refrigerantreaches the condensor,the molecules turn intoliquid again and areless free to move

Meat, vegetables and dairy products alllast longer if kept in a fridge

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What temperature should thefridge be inside?

It is important to make sure that your fridge is kept atthe correct temperature – too warm and harmfulbacteria will start to grow; too cold and your foodmight become frozen! The perfect temperature for theinside of a fridge is between 0–5°C, so check yoursregularly!

Compressor – this takesfumes from the evaporator,and ‘squashes’ the gasusing electricity, increasingthe pressure

Condenser – this allows thegas to cool and turn into aliquid, releasing heat throughcooling fins on the back ofthe fridge

Defrost tray

Freezer compartment

Temperature controls

Compressor

Defrosttray

Inner doorshelving

When you open the door of a fridge, it’s hard to believethat there’s lots of action going on at the back to keepthings cool.

Ice rinks also use pipes containing refrigerant, just like afridge. The pipes run through the concrete base of the rinkwhich is flooded with water to make the ice.

FACT BYTES

Fridge compartmentEvaporator

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The bottom of each of the pistons is attached to a shaft(a metal rod) called a crankshaft. They are fastened insuch a way that the constant up-and-down movementmakes the crankshaft turn around and around. Thiscrankshaft is linked to another shaft called the drive-shaft, which makes the wheels go round. A connectingrod rotates at both ends, its angle changing with themovement of the piston and the rotation of the crankshaft.

Many motor cars are powered by petrol engines, which use cylinders containingpistons to convert fuel into movement. Most petrol cars use four-stroke engines –meaning that there are four strokes, or stages, to making the engine turn the wheels.So, what happens after you turn the electric starter motor on?

What do the cylinders do What makes the car move

PETROL ENGINE

The motor moves four cylinders in stages, eachcontaining a ‘piston’ (see main diagram). Piston 1moves down, sucking in petrol vapour and air. Piston2 moves up, squeezing the mixture into a smallerspace, putting it under high pressure. Inside Piston 3 a mixture of petrol and air is ignited. This causes anexplosion, pushing the piston back down. Finally,Piston 4 moves up, pushing the exhaust gases out.

Piston

Crankshaft

As the pistongoes up

and down,the crankshaftmoves around

Underneaththe bonnet of a car is the engine

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Cylinder – air and petrol are mixed inside these,and the force moves the pistons up and down

Crankshaft – creates a ‘roundand round’ movement

Gearbox – differentgears make thewheels turn at different speeds

Exhaust manifold –contains inlets andoutlets to take gasesto the exhaust pipe

Below: The driver starts the car byturning the ignition key (found nearthe steering wheel).This starts the electricmotor, providing powerto set the pistonsin motion

Spark plug – makesthe mixture of fuel andair in the pistonexplode, and movesthe piston down

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Some cars have more than four cylinders so they runfaster or more smoothly. Expensive cars have eight oreven twelve cylinders in their engine. Instead of beingset out in a long row, which would take up a lot ofspace, they are lined up in V-shaped pairs, so theyonly take up half the space.

Do all cars have the same number of cylinders

What does ‘fuel injection’ mean

In many older cars, stage 1 of the four-stroke processrelies on a carburettor, which mixes the petrol vapourwith air to get the right mix to make the car workefficiently. However, modern cars use fuel injectioninstead of a carburettor. This fuel injection iscomputer-controlled to squirt precise amounts of neatpetrol into the cylinder.

A tiny amount of fuel,squirted into the cylinderinside the piston,releases a huge amountof gassy energy. An electric fuel injectorimproves a car’sperformance.

The fastest car in the world is driven by a jet engine (seepages 30–31), not a petrol engine. However, Formula Onecars use 2.4 litre petrol engines, and can reach speeds inexcess of 320 kph (260 mph) – that’s prettyfast! Every F1 car is capable of goingfrom 0-160 kph(100 mph) and back to 0 in lessthan 5 seconds.

FACT BYTES

The most powerful cars have more than four cylinders

The nozzle creates a fine mist of fuel,which will burn easily.

Smokestack

Boiler – this is afire tube boiler,common in the1800s. The tankof water is filledwith pipes, whichheat the waterinside

Heattravels toboiler

The fuel (coal)is burned inthe furnace

The high-pressure steam iscreated inside a boiler

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Steam has been used to create power since the first century AD, when aGreek mathematician and inventor called Hero built a tiny steam engine. Thesteam engine wasn’t revisited properly until the 1700’s – and when it was, itproved to be the dominant source of power well into the twentieth century.

Who invented the steam engine

STEAM ENGINE

Thomas Newcomen created the first practical steamengine for pumping water, in 1712. James Watt(1736–1819) then improved this earlier invention.Previously, the steam entered heated cylinders, which

then had to be graduallycooled (this condensed the steam). Watt patented amore efficient separate

condenser, removingthis heating andcooling process,thus making theengine work muchfaster.

An early steamengine

Boiler

Valverod

Exhaust

Piston rod Piston

Drive rod

High-pressuresteam in

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Fuel, usually coal, is fed into a furnace (the placewhere the fuel is burned) and set alight. The hotgases, which are produced by the fire, are directedalong pipes through a boiler, where they heat upwater inside a tank. This causes the hot water to turninto steam, and if steam is further heated, its pressurerises and it can be used to force a piston along acylinder. This moving piston is linked to the machine,which needs the power.

How do steam engines work

Before makinghis massiveimprovements tothe steam engine,James Watt wasemployed as amaker of mathematicalinstruments.

FACT BYTES

High-pressure steam provides power to machinery

In 1845, the SSGreat Britain was thelargest and fastest shipin the world. Its enginewas powered bysteam produced fromseawater in theworld’s largest boilerat the time!

FACT BYTES

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In 1769, French engineer Nicholas Cugnot inventedthe first self-propelled road vehicle, a militarytractor powered by steam. Able to travel at 4 kph(2.5 mph), it had to stop every fifteen minutes to buildup enough steam to power it further. Cugnot’s secondversion of the vehicle crashed, resulting in him beingimprisoned for causing a danger!

Who invented the first self-propelled vehicle

Nicholas Cugnot’s steam-propelled military tractor

One of the first steamengines was built in1712 by ThomasNewcomen, and its jobwas to pump waterfrom below ground tomines. Many of thesteam enginesdesigned by JamesWatt were used to provide power in factories. In 1802 ahigh-pressure steamengine, invented byRichard Trevithick, ledto the development ofsteam trains.Nowadays, steam is usedto drive turbines, whichgive power to ships andgenerators in power stations.

What are steamengines used for

Power stations usemassive turbines

The first modern steam locomotive (the front part of thetrain which pulls the carriages) was invented in 1829by George Stephenson. He won £500 for building hisfamous locomotive Rocket (below), which reached aspeed of 46 kph (29 mph).

When was thelocomotive invented

Scientists knew that a jet of air streaming backwards could be used to pushan object forwards. It’s just like an open-ended balloon flying around theroom. They then used this knowledge to make an engine …

When was the jet engine invented

JET ENGINE

In 1929, engineer and test pilot Frank Whittle putthe ‘open-ended balloon’ theory to the test. He sawthat air put under pressure and burnt with fuel couldproduce the energy needed to power a plane. Hecouldn’t persuade the British Air Ministry to use hisidea, so set up his own company to develop it. In1941 he successfully made an aeroplane fly using thepower of a jet engine, and others were quick to follow.

In 1948, King George VI bestowed a knighthoodon Whittle (above), for his contribution to thefuture of flight

How does it work

Fan TurbineBlades

Fans at the front of the engine spin and suck in air.Blades inside compress (squash) the air and force itinto a combustion chamber. Inside this chamber,liquid fuel is burnt to heat up the pressurised air, whichmakes it expand. It rushes out of the back of theengine, and over a turbine, which keeps the fans atthe front turning. The force created by the rushing airpushes the engine and vehicle forwards.

The fan sucks in air and the blades compress it

Inlet – bringsin air fromoutside theengine

Fan – sucksair in fromthe inlet

Shaft – connectsthe compressorto the turbine

Blades – ‘airfoil’ shaped – a designwhich minimises drag forces

Burner – wherethe fuel and theair are mixedand burned

Nozzle – made in a special shape to ensurethat as little of the hot exhaust gas is lost, andthat it passes through as quickly as possible. Italso helps to keep the flow of fuel constant

Turbine – thiskeeps the fans atthe front moving

Combustion chamber

Compressor – increases the pressure ofthe incoming air before it enters thecombustion chamber

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Where are jet engines used

Jet engines are most commonin large passengerplanes or fast fighterplanes. A type of jetengine called a gasturbine is used topower some tanks,helicopters and even powerplants! Jet engines are also foundin jet-propelled cars, such as ThrustSSC, designed to be the fastest caron land.

Why do planes havetwo engines

Most passenger planes have at least two engines – butthey don’t need both of them to fly safely. The planesare designed so that if one engine stops working, theplane can still fly using the other engine, until itreaches somewhere to land for repairs.

Two engines make aeroplane flight even saferThe jet-propelled Thrust SSC

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The gearbox inside a car is a very complicated arrangement of turning cogsthat turn all of the forces present in a car into movement. Gears are usedeverywhere, from egg whisks to chainsaws – so let’s look at the basics.

How do gears work

GEARBOX

Gears are used in many machinesto change their speed or poweroutput. These can be as simple asthe gears in an egg whisk. Alarge gearwheel is next to a smallgearwheel, with their teeth linkedtogether (see main diagram). If youturn the handle on the large wheel,the linked teeth make thesmall wheel turn, too.However, the small wheel turns fasterthan the large one. If you move thehandle to the small wheel and turn it,it turns the large wheel slowly, butwith more force.

What types of gearbox are there

When the gearstick is moved, it changes the connectionsin the gearbox to give combinations of differentgearwheels. Bottom gear gives the highest turningforce but the lowest speed, allowing the car to startmoving when stopped, e.g. at traffic lights. Moving upa gear reduces the force, but increases the speed.Some cars, called ‘automatics’, use hydraulics toproduce different gear ratios amongst one set of gears.

You will find a simple gear set-up in the cogs ofan egg whisk, where the gears get the forcerequired to turn from your hand movement. Thegears in a car are more numerous and are linkedto other sets of gears

Above: an automaticgearstick. Above right: afive-speed gearstickRight: a six-speedgearstick, used in‘performance’ cars

Teeth – controlthe gear ratio.The number ofteeth in gear2 (20) is exactlytwice that ofgear 1, (10)giving a ratio of 2:1

Gear shaft – the gears are fixed closelyto the shaft, which is turned to make thegears go round. The shaft adjusts therotation of the gears

‘Performance’ carsoften have six gears.This makes the distancebetween gear ratiossmaller and moving upand down the gears is smoother.

FACT BYTES

The relationship between different gears is known as the ‘ratio’. Gearone (top) has half the diameter of gear two (below). Gear one needs toturn twice to cover the same distance as gear two. Thus, these gearshave a ratio of ‘2:1’

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This shaft andgear are connected tothe clutch

Layshaft – gears spin as oneunit and are connected tothe engine

Towheels

Fromengine

How is a gear selected

The parts on the ‘collar’ don’t have to be connected toanything. When the car is in ‘neutral’, all the parts canmove without connecting the engine to the shaft thatturns the wheels. If the gear stick is moved out of neutral, this connects one of the collars by slotting thedog teeth on the front or back into holes on the sidesof the gear wheels.

Collar – connects gears tothe drive shaft. It can slidealong to engage them

This links the gearbox and theengine and lets you connect /disconnect the wheels. Pressingthe clutch pedal moves theclutch plate away from theengine, giving you time tochange gear while the engine runs.

What does the clutch do

‘Dog teeth’ – slot into theholes in the gears to‘engage’ them

Gearselectorfork

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The clutch plate

The computer is one of the most amazing inventions of recent times. Todaythey are everywhere, in schools, offices and homes throughout the world.Let’s have a look at the main parts.

What is a motherboard

It’s just a name for the main circuit board inside thecomputer. It is covered with tiny electrical components,and contains the CPU (central processing unit) which islike the computer’s brain. The memory is usually on themotherboard, too – but you’ll hear people talk abouttwo different types. RAM (random access memory) islike a ‘long term’ memory. Like you, the computer canlearn something and recall it when needed – just likeyou can recall how to ride a bike when you need to!ROM (read only memory) stores major information likewhat to do when the computer starts up.

COMPUTER

What is the hard drive

The hard drive is a sealed unit containing several diskscovered with a magnetic coating. These work likeCD-ROMs or DVDs to store and transfer data, but theycannot be moved from one computer to another. Thehard drive contains all the important information thatallows your computer to store documents and files, andrun your programs.

CD drive

Hard drive

Ribbon cable – joins themotherboard and otherelectronic parts to the hard drive RAM slots – located on the motherboard

Cooling fan

Powerbutton

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The motherboard is one of the main partsof a computer

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Cathode ray tube – a filamentfocuses a beam onto the screen,and phosphor makes it glow

Screen – this contains thousands of tinyparticles called pixels, which join togetherto make the picture

Monitor buttons

Monitor

A monitor, or visual display unit, allows informationfrom the computer to be seen

How does a mouse work

There are two types of mouse. One has a ballunderneath that rolls around when you move themouse. The ball is connected to wheels inside, whichtell the computer where you have moved it. The othertype uses a red light to follow your movements andsend signals to the computer.

Function keys –can be programmedto do special commands

Space bar

Protective layer

Key contacts Electroniccircuits

Keyboard cable

What does the keyboard do

The keyboard allows the user to type letters, numbersand characters into a computer. It is joined by a cableto the central processing unit (CPU). Electronic circuitsunderneath the keys carry messages to the hard driveso that ‘commands’ are carried out. The keys are programmedto carry out a varietyof instructions.

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It wasn’t until 1946that a recognisabledigital computer wasinvented, at HarvardUniversity in the US.Amazingly, it was thesize of a whole room!Technology has comea long way since then!

FACT BYTES

Control keys– carry outspecificinstructions

The undersidesof an opticalmouse (top)and atrack-ballmouse

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Inside, a small laser beam points at the spiral on theDVD. The laser moves gradually from the inside to theoutside edge in a straight line. As the disc spins, thelaser reads every part of the spiral as it passes over it.The bumps in the spiral make the laser bounce off thedisc in different ways, and a sensor reads the changein the light and turns it into an electrical signal. This isturned into sound waves and images and a pictureappears on your screen!

How about watching your favourite film, listening to your favourite song or storing your favourite photos … a Digital Versatile Disc (DVD) can do all this!

What is a DVD made of

How does a DVD player work

A DVD has an inner layer of clear plastic calledpolycarbonate plastic. The information is recordedonto one side of this in a very thin spiral, starting nearthe centre and travelling out to the edge of the disc.The spiral is made up of microscopic bumps, whichcan be read by a laser inside the DVD player (seediagram). Over the plastic is a shiny aluminium layer,which has an acrylic coating on top to protect it. Thisallows a label to be printed onto the disc without spoil-ing the information underneath.

DIGITAL VERSATILE DISCS

Label – made froma sticky piece ofspecial paperwhich allows youto print any information on it(such as the nameof the film)

Acrylic – this issprayed onto thealuminium layer toprotect it

Aluminium – athin, reflectivelayer is added, ontop of the polycar-bonate moulding

Polycarbonateplastic – this layeris covered in ‘pits’on the aluminiumside, but ‘bumps’on the side thelaser reads

Video cassette recorders were used before DVDs. Theinformation is kept on tape, which is pulled out to fitaround several heads and drums. These read theinformation, feed the tape through the machine at thecorrect speed and rewind the tape at the end. Themain parts are the audio head, which reads the sound-track (both musicand words) and thehead drum, whichreads the informationneeded to produce apicture on screen.

What came before DVDs

Drive motor – spins the disc at the correctnumber of revolutions (spins) per minute.This has to work with the laser ‘reading’

the DVD so that theyare in sync witheach other

Disc drive – the DVDenters through a thinslot or tray, and isheld here

Laser lens – thelaser projects through here,and ‘reads’ the bumps in the DVD

Tracking motor –along with thetracking drive, thismoves the laser sothat the beam follows the spiraltracking at theright speed

When you are watching a favourite film, it can bevery irritating when the same part of the film ‘skips’,meaning it stops for a very short time and thencontinues playing at a later point. This usually meansthat the DVD has been damaged. The pits on the datatrack may have been distorted in shape, so that thelaser has to ‘jump’ over them. Sometimes, this is simplycaused by a fingerprint or a dirty mark, which can bewiped off with a cloth.

Why do DVDs ‘skip’

Video cassettes played films before DVDs

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Shhh, settle down, it’s time for your favourite show – but what exactly goeson inside that box when you flick the on / off switch on your remote control?Painting by pixels and a whole lot more!

What’s inside atelevision set

Most TVs consist of a cathode ray tube (CRT), whichbeams electrons onto a phosphor-coated screen thatlights up when the electrons hit it. The picture isactually a rapid sequence of tiny dots, which are‘painted’ by the electron beam, which moves acrossthe screen sixty times every second.

TELEVISION

How do the programmesget to my house

Standard TV programmes are sent to your home aselectric (analogue) or digital signals beamed throughthe air. They are first sent along a cable to huge TVmasts which broadcast the signals to a wide area.The aerial on your house, usually on the roof, picks upthese signals and sends them into your TV. The TV canthen turn these signals back into sounds and picturesto display them on the screen.

TV signals travelthrough the air

What about satellite andcable television

Many people pay for extraTV channels, which are sentunderground along cables,or beamed around theworld using satellites. Tostop people getting extrachannels for free, thesignals are ‘scrambled’ andwon’t work unless you havea receiver box.

Over the next few years, manycountries will switch over todigital. Analogue signals willbe switched off, leaving onlythe digital signal. Oldertelevisions (right) do not‘speak’ digital language, somay need help with a digitaldecoder, in the form of a box.

FACT BYTES

A satellite dish picks up signalsfrom satellites orbiting earth

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Inside is a circuit board with an LED (light emittingdiode) – like a light bulb – at the end. Each time youpress a button, a circuit goes around inside, and a signal is sent from the LED as aray of infrared light. YourTV receives this ray oflight and knows whichbutton was pressed, andacts as if you had pressedthe same button on the TV.

How does a remotecontrol work

Why do people buyplasma screens

Plasma screens take up much less space, as the CRT isreplaced bygas-filled, phosphor-coated ‘bubbles’sandwiched betweentwo plates of glass.Plasma screens areonly around 15 cm(6 in.) thick and canbe hung on the wall!

Cathode ray tube –beams electrons fromthe back of the tubeonto the screen. It worksin a similar way to theheated filament in alight bulb

Electron beams –colour TVs usered, green andblue beams tomake up afull-colour picture

Shadow mask – athin metal sheetwith tiny holes isplaced behind thescreen and eithersingle orcombinations ofcolours are ‘fired’through

Screen – whenthe electronbeams hit thephosphor-coatedscreen, it glows

A remote control sendsmessages to the set usinginfrared light

Frontplateglass

Plasma‘bubbles’

Rearplateglass

A satellite is any object that orbits or revolves around another. In addition tothe Moon (a natural satellite), thousands of man-made satellites also orbitEarth. They are used for many different purposes, including satellite television,phone calls, radio transmissions, Internet connections, weather forecasting,scientific research and surveillance.

How high are satellites

SATELLITES

Many scientific satellites are only 300–400 km (185–250 miles) above Earth and orbit in under two hours. As thesesatellites are relatively close to Earth, they require littlefuel and are cheap to launch. Major communicationssatellites are put at a huge distance of 36,000 km(22,369 miles) from Earth. At this distance, an orbittakes exactly one day to complete. Satellites have alsoorbited the Sun, Moon, asteroids and some planets.

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300–400 km36,000 km

How many man-made satellitesare out there

Man-made satellites are also called ‘artificialsatellites’. Since the late 1950s, thousands of satelliteshave been launched. Many of the early satellites havefallen back to Earth and burned up in the atmosphere.There are also thousands of items of ‘space-junk’,such as rocket boosters and fuel tanks that have notburned up in orbit. Today, there are about 3,000useful satellites and 6,000 pieces of ‘space junk’orbiting Earth.

Why do satellites burn up

Many satellites do not remain in their orbits, butgradually return to Earth. As a satellite loses altitude(height) it enters denser regions of the atmosphere,where friction between the satellite and theatmosphere generates a great deal of heat. The airaround the satellite becomes so hot that pieces of thesatellite break into smaller pieces, eventually burningup or disintegrating. Some satellite components cansurvive the re-entry heating, crashing down to Earth attremendous speeds!

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‘Space junk’ – debrisfrom broken upsatellites

This contains propellant and allthe instrumentsrequired to sendinformation to Earth

Satellites may also contain x-ray detectors

High gain antenna –provides the satellite withradio control

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Before radio was invented, the best way to send messages to remoteplaces or to ships in the middle of the ocean was to fasten a note to the legof a pigeon!

Who invented the radio

Many inventors contributed towards the creation of theradio, but Italian Guglielmo Marconi played animportant part in developing the use of radio wavesfor transmitting sound and information, and madehuge steps in radio communication around the world.However, a Croatian-born American, Nikola Tesla, isnow credited with the invention of the modern radio,after his 1943 patent was granted instead of Marconi’s.

RADIO

How does a signal reach the set

Radio signals travel through the air aswaves, which can carry sounds from atransmitter (a mast which sends outsignals) to a receiver (an aerial onyour radio). The aerial on the radio(right) picks up more signals than theinternal receiver on the model in themainpicture, but both allow you to tune inyour radio to a frequency that will pickup the signal.

GuglielmoMarconi

Nikola Tesla

FACT BYTES

On 18th June, 1940,Churchill’s uplifting speechwas heard by British peoplethrough radios like this one.It encouraged them throughthe ‘darkest hour’ of WorldWar II and promised apolicy of ‘no surrender’ toNazi forces.

Battery – contains two‘terminals’, with thecurrent flowing fromone to the other

Speaker – the soundwave moves a coil,which causes adiaphragm to vibrateand produce soundthrough the front

Circuit board – contains transistors,used to turn radiosignals into sound

Internalreceiver –picks upthe signal

Frequency gauge – a needle movesalong to show the various frequenciesto which you can tune the signal

Volumecontrol

This radiowas producedin the 1960s byRoberts Radio Co. Ltd.In 1939, Queen Elizabeth IIwas bought a ‘Roberts’ by her mother

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What other inventionsuse radio waves

It’s amazing that radio waves play an important partin lots and lots of modern pieces of equipment.Without our knowledge of radio waves, we wouldn’thave walkie-talkies, cordless phones, radio-controlledtoys, garage-door openers, mobile phones, radar …and we wouldn’t be able to fly safely in an aeroplane,microwave our food or watch satellite TV!

Radio is also important for ships and militaryoperations, allowing people to communicatewherever they are

Tuner – use to adjust thefrequency

On/off

Inventors had tried to perfect a ‘sum machine’ for many years, resulting in theinvention of the pocket calculator in 1966. It’s tempting to let calculators do allthe ‘head work’ for you, but you still have to input the numbers correctly!

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CALCULATOR

Who invented the moderncalculator

Several inventors created ‘adding devices’. BlaisePascal devised a machine in 1642, which worked byturning dials, and Charles Babbage invented a‘computer’ in 1834, which was a huge machine forsolving maths problems. However, it was US companyTexas Instruments who brought the modern, hand-heldcalculator to the market in 1967.

Blaise Pascal Charles Babbage

What’s inside a calculator

A simple calculator has a keypad so that you canenter numbers, with a circuit board situatedunderneath. On the circuit board is the LCD (liquidcrystal display) so that you can read the answers, asolar panel (which converts light into energy) and amicroprocessor. Like a tiny computer, this contains acomplicated set of circuits, which carry out your sums!

What were old calculators like

The first electronic calculator was manufactured in1961 by the Bell Punch Company, and was calledANITA. Before this, any calculating machine useda series of gears and number wheels instead ofelectronics. ANITA wasstill huge, even thoughit worked electronical-ly. It was called adesktop calculatorbecause it certainlywouldn’t fit into yourpocket like modern ver-sions.

Keypad – the keyson the keypad turnyour sums intocommands thatthe calculatorunderstands

LCD – a number is producedby a group of segments linkedto the solar cell. It is not untilthe electric signal passesthrough that each segmentdarkens to create the number

Microprocessor –contains a silicon chip,made from manylayers, which areexposed to chemicalsand electronicallycharged

Solar cell – if there is enoughlight, a circuit causes the LCDdisplay to appear

Push button key contacts – whenthe keys are pressed, they carrymessages via the circuit board tothe microprocessor

Each digit is made fromlittle segments whichmake the numbers 0–9

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Why are the numbers arranged inthe opposite order from a telephone

It’s possible that toavoid people diallingtoo quickly (and getting wrongnumbers), the telephone padwas changedfrom the familiarcalculator padwhich came‘first’.

All the calculator needs to know is four binary sums:

1) 0 + 0 = 0 2) 0 + 1 = 1 3) 1 + 0 = 14) 1 + 1 = 10 (which, if you see below, is 1two and 0 units – i.e. 2)

The calculator changes all of its numbers into binarywhen they are punched in on the keypad, adds themup in binary, and then displays them on the screen indecimals again so that you can understand it straightaway. Try doing a binary sum yourself:

1 1 0 0 + 0 0 1 1 = 1 1 1 1(in decimals, 8 + 4 + 2 + 1 = 15)

You see why it’s so easy for the calculator to do sumslike this?

How does the calculator usebinary

Let’s start with the decimal system, based around multiples of ten (1,10,100 and so on). Breaking down the number 356, we can see it is actually:

Hundreds Tens Units (ones)

3 5 6

(300 + 50 + 6 = 356)

In the binary system, the column headings are multiples of two (1, 2, 4, 8and so on). So the number 13 looks like this:

Eights Fours Twos Units

1 1 0 1

(8 + 4 + 1 = 13)

What does the binary system look like

Scientists at IBM’sresearch laboratoryin Zurich,Switzerland, havedesigned acalculating devicewhich has adiameter of lessthan 0.000001mm (39/100 in.)

FACT BYTES

Compare this telephone keypad to the one onyour calculator

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The basic make-up of the telephone has not changed a great deal since itsinvention in 1876. The handset consists of a mouthpiece, containing amembrane that vibrates when you speak into it, and an earpiece, whichcontains a loudspeaker.

Who invented the telephone

Alexander Graham Bell (right), a Scottish scientist,invented the telephone in 1876. He spoke the firstwords ever heard on a telephone. He said, ‘MrWatson, come here; I want to see you.’ It must havebeen a surprise to Mr Watson who didn’t know what atelephone was!

TELEPHONE

What is inside a telephone

A telephone consists of three main parts. The mouth-piece contains a microphone, which turns the soundwaves into electric signals. The earpiece contains asmall loudspeaker, which turns the signals back intorecognisable sounds, loud enough for you to hear.The dialling keys send an electronic message to atelephone exchange. This exchange knows whatnumber you dialled and connects you to the correctphone wherever it is around the world.

How can I speak to peoplein other countries

It is possible to speak, bytelephone, to people allaround the world by theuse of satellites orbitingEarth. They communicatewith ground stations byradio, sending andreceiving information.This includes soundsignals, such as voiceson telephones.

A satellite dishreceives signalsfrom orbitingsatellites in space

Control circuitshave advancedrapidly, allowingmany lines ofcommunication tobe open at once

Control circuits – whenyou push the buttons,the chip circuits sendcoded messages tothe telephone exchangeand connect you tothat number

Earpiece – the signal passes through,causing a tiny electromagnet tovibrate, touching a membrane thatmagnifies the sound

Push buttons – linked tothe control circuits

Mouthpiece – whenyou speak, yourvoice vibrates,squashing granulesof carbon inside tovary the level ofelectric currentpassing through

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‘Mobiles’ are more like a radio than a phone.Standard telephones send their signals along cables –but you can’t drag a cable behind you as you walk!Instead, mobile phones use radio waves to carry yourvoice (see page 44–45). The clever part is that theyconnect to different radio transmitters as you movearound. Mobiles are also ‘duplex’ devices, whichmeans that they use one frequency for talking andanother for listening, so you can do both things atonce. Walkie-talkies, for example, are half-duplexhandsets, which only let you do one of these thingsat a time.

How do mobile phones differ from other talking devices

What is a ‘cell’ phoneFACT BYTES

British Telecom Tower inLondon can deal with upto 150,000 telephone callsbeing made at the sametime! It is a relay tower,which uses microwavesinstead of cables to sendtelephone messages quickly and efficiently.

To allow you to move around whileyou’re talking, there are manyradio transmitters in every region.Each of these transmitters is in itsown small area, roughly theshape of a hexagon. All thehexagons fit together ina regular pattern, like ahoneycomb, called acellular network. Ithas become commonfor each hexagon to becalled a cell. The clever thing is,your phone picks up the differenttransmitters as you move around, without evenaffecting your phone call!

If radio transmitters are too far apart,we lose our mobile signal

A radio transmitter, or mast,receives signals from mobile

phones and transmits them toother mobiles or networks

The light bulb … something that we all take for granted, but it has only existed sincethe late 1870’s. Since then, manufacturers have produced many types of light bulb,which have built upon this fairly simple, yet brilliant, technology.

LIGHT BULB

When was the very first lightbulb invented

Back in 1802, Humphry Davy made use of the factthat current passed between rods of carbon make alight source. However, his creation was very unreliableand nothing like the light bulbs we use today. Twopeople invented the modern light bulb at the sametime! An Englishman, Sir Joseph Swan, and anAmerican, Thomas Edison, were both working onsimilar experiments in the late 1870’s. By 1881 theyhad joined forces as the Edison and Swan UnitedElectric Light Company.

Thomas EdisonSir Joseph Swan

What is inside a light bulb

Many bulbs contain a thin metal wire, called afilament, together with gases. When you flick the lightswitch, electricity passes through the filament andheats it up until it glows and gives off light. Modernbulbs use a tungsten filament. The gases in the bulbare non-reactive (called inert). These are better thanair because they stop the filament from burning awaytoo quickly.

What are energy efficient bulbs

Filament bulbs waste a lot of energy in the form ofheat, rather than light. Think about how hot a bulbgets after it has been switched on for a few minutes.Energy efficient bulbs don’t waste as much energy

through heat. Many of thesebulbs have been developedwith a phosphorescentcoating on the inside whichglows. They’re the mostefficient of all. This tube or ‘strip’ light is ‘energy efficient’

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Some lighthouses usebulbs twenty timesbrighter than those inyour home. Specialmirrors help reflectthe bright light farout to sea – thiswarns ships that theyare close to land.

FACT BYTES

Flicking theswitch allowsthe electricity

to flowthrough thefoot contactand into the

filament tomake it glow

Inert gas (usually argon) – this fillsthe inside of the bulb

Bulb – usually made of glass

Glass mount – holds thefilament in place

Insulation – reducesthe amount of heatthat leaves the bulb

Tungsten filament – electricityflows through this to make thebulb glow and can withstandextremely high temperatures

Screw thread contact – manylightfittings have a base intowhich the bulb can be fixed

Electrical footcontact – connectsthe bulb to thesource of electricityso that it can flowthrough the filament

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CAMERA

What is a camera

A camera at its simplest focuses light onto film to makean image. Old-fashioned ‘camera obscuras’ used alens to project the image of a whole landscape onto ascreen in a darkened room. Standard cameras focusthrough a lens to record an image as a single photothat you can take away.

An example of a cameraobscura. The image isreflected onto the mirrorupside down, then reflectedthe right way around bythe second mirror

Mirror takes in theimage upside-down

Lens

Light entershere

FACT BYTES

This is an example of one of the traditional ‘folding cameras’that were produced around 1900–1920. They held glass

plates, which were loaded into a wooden holder. This holder slid into a ‘viewfinder’with an additional focusing scale. If you could

estimate how far away the subject wasthen you could set the scale to get asharper image. With a wood-and-brass finish, this type of camera ishighly collectable.

What goes on inside a film camera

Look at the diagram and you can see how the lightbeams enter the camera and make their way onto thefilm. The light is sent through different lenses andprisms and bounced off mirrors to focus the largeoutside image onto the film inside the camera. Bytwisting the front of the camera, you are moving thelens inside to get the image ‘in focus’ – that is, atexactly the right distance to look clear and crisp onthe film. When you press the button to take the photo,the shutter at the back of the camera moves out of theway, allowing light to land on the film. Chemicals onthe film react to the light and record the picture.

Today, you can buy many different sorts of camera: digital, single-use,automatic, SLR (Single Lens Reflex) … cameras have come a long way sincethe first camera obscuras were invented hundreds of years ago.

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This is a diagram of an SLR camera. A mirrormoves out of the way when the photograph isshot, which reflects light onto the ‘pentaprism’ (aprism with five sides). This puts the image into theviewfinder

The SLR was developed in the 1930s, following‘twin lens’ cameras. They used separate lenses forthe picture and viewfinder, and were quite bulky

Camera body

Subject

Viewfinder Mirror orpentaprism

Translucentscreen

Shutter Mirror

Lightpath

Lens

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What is a digital camera

A digital camera takes a photograph digitally, byrecording images via an electronic image sensor,which converts the image into an electrical signal,rather than a chemical one (like a film camera).Digital cameras can display images on a screen immediately after the picture has been taken, storehundreds of pictures and even record videos.

Sophisticated digital cameras like this one can editand enhance images before they are transferredto a computer

How is the picture developed

The small roll of pictures is taken out of the camera.The picture colours are in ‘reverse’ i.e. everythingblack should be white, and vice versa. These are the‘negatives’. The use of an enlarger brings them to theright size, and the light from it transforms the coloursto reverse them. The image is developed and fixed.

Colours in the negatives are reversed, enlarged, and then chemicals are applied to reveal the picture

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An X-ray machine basically works like a large camera, taking pictures using invisiblelight, which passes through solid objects, the ‘charged’ particles exposing things inside.Some substances allow X-rays to pass through them more easily than others.

When were X-rays discovered

The rays themselves were discovered by WilhelmRöntgen in 1895. Once he’d discovered them, hesoon figured out a way of using them to take aphotograph. The first ever X-ray was of his wife’shand, which clearly showed her bones and herwedding ring. Medical scientists were soon usingX-rays for detecting injuries and illnesses.

X-RAY MACHINE

Wilhelm Röntgen

A modern X-ray of a hand

Are they dangerous

X-rays aren’t dangerous if you’re only exposed to themfor a few minutes. However, people who work withand are exposed to X-rays all the time (known as radiologists) have to be careful, and will leave theroom whilst an X-ray photo is taken.

What do X-rays do

X-rays have more energy than normal light rays –enough energy to pass through many substances.They can pass through skin, fabric and many plastics.However, they can’t pass through metal or bone.That’s why an X-ray photograph sees straightthrough bodies and bags and shows brokenbones and metal items – like coins orscissors in your rucksack or fillingsin your teeth.

X-rays can passthrough many plastics, like the oneused on the case ofthis radio, so thatwe can see inside

A person having X-rays taken using a modern machine

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In 1975 Robert SLedley was granted thepatent for CAT scans,which allow the wholebody to be photographed in 3D.The X-rays ‘cut’ what-ever they’re aimed atinto ‘picture slices’,which allows doctorsto see the whole of aperson’s inside!

What are CAT scans

Robert S Ledley

The parts of the brain are easily seen in this CAT scan

Light is an energy source that travels in waves, muchlike water. It’s what allows us to see things around us,and gives objects their colour as we see it. Otherforms of energy travel as waves, too, such asmicrowaves (see pages 10–12) and ultraviolet (UV)

waves, which give us a suntan. X-rays are part of thisseries of waves (called the electromagnetic spectrum),as all the types of waves are electromagnetic, andthey’re very powerful.

What is an X-ray

X-rays are found to the right of the UV rays in theelectromagnetic spectrum

All sounds travel through the air as waves, very muchlike ripples on water (except you can’t see them).These waves bounce against your eardrum and areconverted into messages to your brain. Your brainunderstands what these waves sound like, and whatthey mean if they are speech sounds. A microphone isdesigned to pick up the same sound waves andconvert them into an electric signal. It can then sendthe electric signals down a telephone line, or into anamplifier to make the sounds louder.

Outerear

Sound waves travelling into the ear

Soundwaves

Middle earInner ear

A microphone isn’t just the glorified lollipop that pop stars sing into. It canalso be a tiny but important part of another piece of equipment, such as atelephone or video recorder. Inventions such as TV, radio, computer and videoare all amazing inventions that use microphones.

How does sound make itsway into the microphone

MICROPHONE

How does a microphone work

Most microphones contain a stationary magnet thatsurrounds a moveable coil. The magnet’s magnetic‘field’ is activated when sound waves come near. Thiscauses the coil to vibrate. Different sounds producedifferent ‘wavelengths’, which cause a thin metal orplastic sheet above the magnet (called a diaphragm)to move at different pressures. Next, wires carry theelectric signal from the coil to a loudspeaker. Thevibrations cause a special cone inside the loudspeakerto move, and turn the signal back into sound.

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Some computers have a microphone attached, whichconverts a person’s voice signals into text. Some are builtinto the computer keyboard, and pick up the sounds in theair. The advantage of this is thatthey are ‘hands free’ and canalso pick up all the other soundsaround! So, who knows –writing your homework mightbecome a thing of the past!

FACT BYTES

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Coil – this vibrateswhen the magnet’smagnetic field isactivated by soundwaves

Diaphragm – made of plastic or metal, this moves at different speeds, dependingon the length of the sound wave

Magnet –produces a magneticfield, which movesthe coil

Wires – carry thesound wavesdown to theloudspeaker, whichamplifies the sound(makes it louder)through a systemof coils, magnetsand a large cone

Some heads pickup as much surrounding soundas possible. Othersaim to pick up justhigher frequencies

Where does the sound go

If a pop star sings into the microphone, the soundmight go to an amplifier (which makes the soundmuch louder) and out through speakers so the audiencecan hear them sing even louder. Speakers work similarlyto a microphone (but in reverse). When the electricalenergy is passed from the microphone through apower cord, a coil moves via a magnet, which pushesand pulls on the speaker cone. This makes the air infront of the speaker vibrate, creating sound. Power cord

Speakercone

Huge speakers allowaudiences of several thousandto hear the sounds from amicrophone loud and clear!

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AirbagA safety device, installed inall modern cars, which automatically inflates if thevehicle is involved in acollision over certain speeds.Binary systemA numerical system, commonin computing, using only thedigits 0 and 1.CAT – Computer AxialTomographyA scanning machine thatprojects X-ray images ofcross-sectional ‘slices’through the brain or othersoft body tissues.CFC –ChlorofluorocarbonA chemical compound offlourine, chlorine and carbon, used in refrigeration systems.CombustionThe process of burning, oftento produce a reaction thatcauses a greater amount oflight or heat to be produced.CPU – CentralProcessing UnitPart of a computer that performs arithmetical andlogical operations on data,and controls the other unitscontained in the system.

Crank A device fitted in manymachines that converts oneaction to another (such as theup / down movement of apiston to the rotation move-ment of the wheels in a car).CRTCathode ray tubes – used todisplay images in televisionsets, the visual display unitsof computers and radarequipment.CursorThe ‘pointer’ on a computerscreen, which is controlledby moving either the mouseor arrow keys.DragThe resistance to themovement of somethingtravelling through matter –such as the forces acting onan aeroplane or car movingthrough the air.Duplex devicesThese allow the user to carryout two things at once, as ina telephone, where you canboth talk and listen (asopposed to a walkie-talkie).DVD – Digital VersatileDiscA device that stores soundsand pictures.

ElectromagneticHaving both electrical andmagnetic properties, as inX-rays, radio waves and lightwaves.ElectronicsA branch of science andtechnology that deals withthe behaviour of electrons(minute particles of matterwith a negative charge foundin all atoms).FrequencyThe number of times that avibration repeats itself in agiven period of time, usuallyone second and measured inhertz.Gear ratioThe number of times thewheel that is doing the ‘driving’ turns the wheel that is being ‘driven’.HertzThe unit used to measure thefrequency of a sound wave,named after physicist GustavHertz.Hot plate The part of an iron thattouches the fabric, coatedwith a metal alloy to helpprevent sticking.

InfraredUsing, producing, or sensitiveto radiation with awavelength just beyond thered end of the visible spec-trum, usually felt as heat.LasersHigh-intensity beams of ultra-red or ultraviolet radiation.LED – Light EmittingDiodeThese give out light when anelectric current is passedthrough. They are used todisplay numerals and lettersin calculators, watches andother electronic instrumentsthat require a self-luminousdisplay.LocomotiveAn engine usually driven bysteam, diesel or electricitythat pulls carriages along railway tracks.MicroprocessorThe most complex of siliconchips, containing huge numbers of transistors.Modulated CarrierWavesSignal carrying waves, inwhich the frequency oramplitude has beenincreased or decreased (asin radio transmission).

GLOSSARY

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GLOSSARYMotherboardA printed circuit board thatcan be plugged into the backof a computer and into whichother boards can be slottedto allow the operation of various systems.NeonA bright, colourless gas, frequently used in illuminatedsigns due to its glowing witha bright light when an electric current is passedthrough it.Nichrome WiresUsed in a toaster, these arespecial wires made of a nickel-chromium alloy thatgets very hot, but does notbecome damaged in theprocess.Non-conductive materialsA substance, such as plasticor wood, that does not allowheat, electricity or sound toflow through well.PixelThe smallest element of theimage shown on a computeror television screen, consistingof a single dot, which maybe illuminated or dark.

Plasma screenA display system in whichred, blue and green lightsare created in every pixel,therefore reducing the needfor space.RAM – Random AccessMemoryA temporary memory available to the user, whichallows programs to beloaded and run, and data to be changed.ROM – Read OnlyMemoryA memory which holds datapermanently and allows it tobe read, used, but notchanged.ResistorAnything that prevents orslows down an electrical current moving through amaterial or component.SatelliteAn object that rotates aroundor orbits another object. Theycan be man-made or natural.

Shadow maskThe very thin sheet of metalplaced behind the screen ofa TV or computer, covered inholes which guide the electron beams to hit the correct colour pixel.Silicon chipsThe joining together of lots oftiny transistors to form integrated circuits that arepacked inside a wafer-thinpiece of silicon. Used in calculators and other piecesof electronic equipment toform the ‘brain’.SLR – Single Lens ReflexA type of camera whichenables the photographer tosee the exact image that willbe formed on the film, bymeans of light entering thelens and reflected by a mirror up to the viewfinder.ThermostatThe electronic device, foundin electric irons and otherequipment, that keeps thecurrent flowing so that thetemperature stays at thecorrect level for the setting.Thrust SSC Thrust Supersonic Car is themost powerful car everdesigned to attack the land-speed record, which it

smashed in 1997. It alsobroke the sound barrier.TransistorThe ‘switches’ inside an elec-trical circuit, which changethe ways in which they auto-matically react to electricity.Tungsten FilamentA hard, grey metal used inmaking steel alloys and thefilaments of electric lightbulbs.TurbineA device that rotates whencertain types of ‘energy’ arepassed through the blades,such as water or steam,which is then converted intomechanical energy to makesomething move.ValveA device used to shut off,start or control the flow of aliquid – like those used in awashing machine.WavelengthThe distance between twocrests in a sound wave.Lower sounds have greaterwavelengths than high ones.

64

INDEXaeroplane 30–31, 45airbag 13–15amplifier 61ANITA 46

Babbage, Charles 46batteries 45Bell, Alexander

Graham 49binary system 48boiler 27British Telecom Tower

51Brother NX-400 18

calculator 46–48camera 54–56, 57carburettor 26CAT scan 59CD-ROM 35circuit board 35, 45clockwork mechanism

45combustion 30computer 35–37, 46,

60condenser 22, 23cordless telephone 45CPU 35crankshaft 24CRT 40, 41Cugnot, Nicolas 29cylinder system

24–26, 27

DAB radio 45Davy, Humphry 52decimal system 48diaphragm 60digital camera 54–56drive shaft 24, 33duplex devices 51DVD 35, 38–39

Edison, Thomas 52electric motor 24electric signal 38, 40,

49electrical circuit 9,

19, 20electromagnetic

spectrum 59electron beam 41engine, aeroplane

30–31engine, car 24–26,

32–34engine, turbojet

30–31

filament 52–53film (camera) 54–56Fleming, John

Ambrose 45furnace 27–29

gas turbine engine 31gears 32–34

hard drive 35

inner cylinder 4infrared light 41iron 7–9

jet engine 30–31jet-propelled cars 31

keyboard (computer)37, 60

laser 38–39LED 41Ledley, Roberts 59light beams 54light bulb 52–53light rays 57lighthouses 53loudspeaker 61

magnetron 10–12Marconi, Guglielmo

44microphones 49,

60–61microwave oven

10–12mobile phone 51motor cars 13–15,

24–26

Newcomen, Thomas27, 29

nichrome wires 21non-conductive

materials 9

outer cylinder 4

Pascal, Blaise 46petrol engine 24–26plasma screen 41power station 29

radio 44–45, 51radio waves 12,

44–45, 51radiologist 57RAM 35refrigerator 22–23remote control 41ribbon cable 35rocket (locomotive) 29ROM 35Röntgen, Wilhelm 57

satellite 40, 42–43,49

Seely, W. Henry 7sensor 13, 38sewing machine

16–18SLR camera 55sound waves 49,

60–61Spencer, Percy 10,

12steam car 27steam engine 27–29steam locomotive 29Stephenson, George

29Strite, Charles 19Swan, Sir Joseph 52

telephone 49–51television 40–41Tesla, Nikola 44thermostat 9Thimonnier,

Barthelemy 16Thrust SSC 31toaster 19–21transmitter 44, 51Trevithick, Richard 29tube lights 52tungsten filament 52turbines 30

video cassetterecorders 39

vibration 60, 61

walkie-talkies 45, 51washing machine 4–6Watt, James 27, 29Whittle, Frank 30

X-ray machine 57–59

How does toast pop up?Why do microwaves cook

‘inside out’? What is a ‘feed dog’?Who invented the computer?

There are 64 pages of bite-size facts, brilliantillustrations and diagrams to tell you loads

of things you never knew about theinventions that we take for granted.

No question is too tough to tackle,and no answer too difficult toexplain. Focus On titles are

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