How Radio Works by nafees

7/25/2019 How Radio Works by nafees

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How Capacitors Work

In a way, a capacitor is a little like a battery. Although they work in completely

diferent ways, capacitors and batteries both store electrical energy. I you haveread How Batteries ork, then you know that a battery has two terminals. Inside

the battery, chemical reactions produce electronson one terminal and absorb

electrons on the other terminal. A capacitor is much simpler than a battery, as it

can!t produce new electrons "" it only stores them.

In this article, we!ll learn e#actly what a capacitor is, what it does and how it!s used

in electronics. e!ll also look at the history o the capacitor and how several people

helped shape its progress.

Inside the capacitor, the terminals connect to two metal platesseparated by a

non-conducting substance,or dielectric. $ou can easily make a capacitor romtwo pieces o aluminumoil and a piece o paper. It won!t be a particularly good

capacitor in terms o its storage capacity, but it will work.

In theory, the dielectric can be any non"conductive substance. However, or

practical applications, speci%c materials are used that best suit the capacitor!s

unction. &ica, ceramic, cellulose, porcelain, &ylar, 'e(onand even airare some o

the non"conductive materials used. 'he dielectric dictates what kind o capacitor it

is and or what it is best suited. )epending on the si*e and type o dielectric, some

capacitors are better or high re+uency uses, while some are better or high voltage

applications. apacitors can be manuactured to serve any purpose, rom the

smallest plastic capacitor in your calculator, to an ultra capacitor that can power acommuter bus. -AAuses glass capacitors to help wake up the space shuttle!s

circuitry and help deploy space probes. Here are some o the various types o

capacitors and how they are used.

Air " /ten used in radio tuning circuits
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&ylar " &ost commonly used or timer circuits like clocks, alarms and

counters

lass" ood or high voltage applications

eramic " 2sed or high re+uency purposes like antennas, 3"

rayand &4Imachines

Capacitor Circuit

In an electronic circuit, a capacitor is shown like this5

hen you connect a capacitor to a battery, here!s what happens5

'he plate on the capacitor that attaches to the negative terminal o the

battery accepts electronsthat the battery is producing.

'he plate on the capacitor that attaches to the positive terminal o the

battery loses electrons to the battery.

/nce it!s charged, the capacitor has the same voltageas the battery 61.7 volts on

the battery means 1.7 volts on the capacitor8. 9or a small capacitor, the capacity is

small. But large capacitors can hold +uite a bit o charge. $ou can %nd capacitors as
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big as soda cans that hold enough charge to light a (ashlight bulbor a minute or

more.

;ven nature shows the capacitor at work in the orm o lightning. /ne plate is

the cloud, the other plate is the ground and the lightningis the charge releasing

between these two et!s say you hook up a capacitor like this5

Here you have a battery, a light bulband a capacitor. I the capacitor is pretty big,what you will notice is that, when you connect the battery, the light bulb will light

up as current (ows rom the batteryto the capacitor to charge it up. 'he bulb will

get progressively dimmer and %nally go out once the capacitor reaches its capacity.

I you then remove the battery and replace it with a wire, current will (ow rom one

plate o the capacitor to the other. 'he bulb will light initially and then dim as the

capacitor discharges, until it is completely out.

In the ne#t section, we!ll learn more about capacitance and take a detailed look at

the diferent ways that capacitors are used.

LIKE A WATER TWER

/ne way to visuali*e the action o a capacitor is to imagine it as a water

towerhooked to a pipe. A water tower


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!arad

A capacitor!s storage potential, or capacitance, is measured in units called "arads.

A 1"arad capacitor can store one coulomb 6coo"lomb8 o charge at 1 volt. A

coulomb is @.07e1 [email protected] 1CD1, or @.07 billion billion8 electrons. /ne a#p

represents a rate o electron (ow o 1 coulomb o electrons per second, so a 1"arad

capacitor can hold 1 amp"second o electrons at 1 volt.

A 1"arad capacitor would typically be pretty big. It might be as big as a can o tuna

or a 1"liter soda bottle, depending on the voltage it can handle. 9or this reason,

capacitors are typically measured in microarads 6millionths o a arad8.

'o get some perspective on how big a arad is, think about this5

A standard alkaline AA batteryholds about 0. amp"hours.

'hat means that a AA battery can produce 0. amps or an hour at 1.7 volts

6about ?.0 watt"hours "" a AA battery can light a ?"watt bulb or a little more

than an hour8.

>et!s call it 1 volt to make the math easier. 'o store one AA battery!s energy

in a capacitor, you would need :,@CC 0. E 1C,CC arads to hold it,

because an amp"hour is :,@CC amp"seconds.

I it takes something the si*e o a can o tuna to hold a arad, then 1C,CC arads isgoing to take up a >/' more space than a single AA battery= /bviously, it!s

impractical to use capacitors to store any signi%cant amount o power unless you do

it at a high voltage.

Applications
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'he diference between a capacitor and a battery is that a capacitor can dump its

entire charge in a tiny raction o a second, where a battery would take minutes to

completely discharge. 'hat!s why the electronic (ash on a camerauses a capacitor

"" the battery charges up the (ash!s capacitor over several seconds, and then the

capacitor dumps the ull charge into the (ash tube almost instantly. 'his can make a

large, charged capacitor e#tremely dangerous "" (ash units and'Fshave warningsabout opening them up or this reason. 'hey contain big capacitors that can,

potentially, kill you with the charge they contain.

apacitors are used in several diferent ways in electronic circuits5

ometimes, capacitors are used to store charge or high"speed use. 'hat!s

what a (ash does. Big lasersuse this techni+ue as well to get very bright,

instantaneous (ashes.

apacitors can also eliminate ripples. I a line carrying ) voltage has ripples

or spikes in it, a big capacitor can even out the voltage by absorbing thepeaks and %lling in the valleys.

A capacitor can block ) voltage. I you hook a small capacitor to a battery,

then no current will (ow between the poles o the battery once the capacitor

charges. However, any alternating current 6A8 signal (ows through a

capacitor unimpeded. 'hat!s because the capacitor will charge and discharge

as the alternating current (uctuates, making it appear that the alternating

current is (owing.

In the ne#t section, we!ll look at the history o the capacitor and how some o the

most brilliant minds contributed to its progress.
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History o" t$e Capacitor

'he invention o the capacitor varies somewhat depending on who you ask. 'here

are records that indicate a erman scientist named ;wald eorg von Gleist invented

the capacitor in -ovember 1?7. everal months later ieter van &usschenbroek, a

)utch proessor at the 2niversity o >eyden came up with a very similar device inthe orm o the Leyden %ar, which is typically credited as the %rst capacitor. ince

Gleist didn!t have detailed records and notes, nor the notoriety o his )utch

counterpart, he!s oten overlooked as a contributor to the capacitor!s evolution.

However, over the years, both have been given e+ual credit as it was established

that their research was independent o each other and merely a scienti%c

coincidence

'he >eyden Jar was a very simple device. It consisted o a glass Jar, hal %lled with

water and lined inside and out with metal oil. 'he glass acted as the dielectric,

although it was thought or a time that water was the key ingredient. 'here was

usually a metal wire or chain driven through a corkin the top o the Jar. 'he chain

was then hooked to something that would deliver a charge, most likely a hand"

cranked static generator. /nce delivered, the Jar would hold two e+ual but opposite

charges in e+uilibrium until they were connected with a wire, producing a slight

spark or shock
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BenJamin 9ranklin worked with the >eyden Jar in his e#periments with electricity and

soon ound that a (at piece o glass worked as well as the Jar model, prompting him

to develop the &at capacitor, or 9ranklin s+uare. $ears later, ;nglish chemist

&ichael 9araday would pioneer the %rst practical applications or the capacitor in

trying to store unused electronsrom his e#periments. 'his led to the %rst usable

capacitor, made rom large oilbarrels. 9araday!s progress with capacitors is whateventually enabled us to deliver electric power over great distances. As a result o

9araday!s achievements in the %eld o electricity, the unit o measurement or

capacitors, or capacitance, became known as the arad .

How Inductors Work

An inductor is about as simple as an electronic component can get "" it is simply a

coil o wire. It turns out, however, that a coil o wire can do some very interesting

things because o the magnetic properties o a coil.

In this article, we!ll learn all about inductors and what they!re used or.

Inductor 'asics

In a circuit diagram, an inductor is shown like this5

'o understand how an inductor can work in a circuit, this %gure is helpul5
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hat you see here is a battery, a light bulb, a coil o wire around a pieceo iron6yellow8 and a switch. 'he coil o wire is an inductor. I you have read How

;lectromagnets ork, you might recogni*e that the inductor is an electromagnet.

I you were to take the inductor out o this circuit, what you would have is a normal

(ashlight. $ou close the switch and the bulb lights up. ith the inductor in the

circuit as shown, the behavior is completely diferent.

'he light bulb is a resistor6the resistance creates heat to make the %lament in the

bulb glow K see How >ight Bulbs orkor details8. 'he wire in the coil has much

lower resistance 6it!s Just wire8, so what you would e#pect when you turn on the

switch is or the bulb to glow very dimly. &ost o the current should ollow the low"resistance path through the loop. hat happens instead is that when you close the

switch, the bulb burns brightly and then gets dimmer. hen you open the switch,

the bulb burns very brightly and then +uickly goes out.

'he reason or this strange behavior is the inductor. hen current %rst starts (owing

in the coil, the coil wants to build up a #agnetic (eld. hile the %eld is building,

the coil inhibits the (ow o current. /nce the %eld is built, current can (ow normally

through the wire. hen the switch gets opened, the magnetic %eld around the coil

keeps current (owing in the coil until the %eld collapses. 'his current keeps the bulb

lit or a period o time even though the switch is open. In other words, an inductor

can store energyin its magnetic %eld, and an inductor tends to resist any change

in the amount o current (owing through it.

THI)K A'*T WATER+++

/ne way to visuali*e the action o an inductor is to imagine a narrow channel with

water (owing through it, and a heavy water wheel that has its paddles dipping into

the channel. Imagine that the water in the channel is not (owing initially.
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-ow you try to start the water (owing. 'he paddle wheel will tend to prevent the

water rom (owing until it has come up to speed with the water. I you then try to

stop the (ow o water in the channel, the spinning water wheel will try to keep the

water moving until its speed o rotation slows back down to the speed o the water.

An inductor is doing the same thing with the (ow o electrons in a wire "" an

inductor resists a c$ange in t$e &ow o" electrons.

Henries

'he capacityo an inductor is controlled by our actors5

'he number o coils " &ore coils means more inductance.

'he material that the coils are wrapped around 6the core8

'he cross"sectional area o the coil " &ore area means more inductance.

'he length o the coil " A short coil means narrower 6or overlapping8 coils,which means more inductance.

utting ironin the core o an inductor gives it much more inductance than air or

any non"magnetic core would.

'he standard unit o inductance is the Henry. 'he e+uation or calculating the

number o henries in an inductor is5

H . / 0i / 1Turns / 1Turns / coil Area / #u2 3 coil Lengt$ / 45,555,5552

'he area and length o the coil are in meters. 'he term #uis the per#eabilityo

the core. Air has a permeability o 1, while steel might have a permeability o 0,CCC.

Inductor Application6 Tra7c Lig$t 8ensors

>et!s say you take a coil o wire perhaps @ eet 60 meters8 in diameter, containing

%ve or si# loops o wire. $ou cut some grooves in a road and place the coil in the

grooves. $ou attach an inductance meter to the coil and see what the inductance o

the coil is.

-ow you park a car over the coil and check the inductance again. 'he inductance

will be much larger because o the large steel obJect positioned in the loop!s

magnetic %eld. 'he car parked over the coil is acting like the core o the inductor,and its presence changes the inductance o the coil. &ost traMc light sensorsuse

the loopin this way. 'he sensor constantly tests the inductance o the loop in the

road, and when the inductance rises it knows there is a car waiting=

How Lig$t E#itting 9iodes Work
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1C

Lig$t e#itting diodes, commonly called >;)s, are real unsung heroes in the

electronics world. 'hey do do*ens o diferent Jobs and are ound in all kinds o

devices. Among other things, they orm numbers on digital clocks, transmit

inormation rom remote controls, light up watches and tell you when your

appliances are turned on. ollected together, they can orm images on aJumbo

television screenor illuminate a traMc light.

Basically, >;)s are Just tiny light bulbs that %t easily into an electrical circuit. But

unlike ordinary incandescent bulbs, they don!t have a %lament that will burn out,and they don!t get especially hot. 'hey are illuminated solely by the movement o

electrons in asemiconductormaterial, and they last Just as long as a standard

transistor. 'he liespan o an >;) surpasses the short lie o an incandescent bulb by

thousands o hours. 'iny >;)s are already replacing the tubes that light

up >)H)'Fs to make dramatically thinner televisions.

In this article, we!ll e#amine the technology behind these ubi+uitous blinkers,

illuminating some cool principles o electricity and light in the process.
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At t$e %unction, "ree electrons "ro# t$e )-type #aterial (ll $oles "ro# t$e

0-type #aterial+ T$is creates an insulating layer in t$e #iddle o" t$e diode

called t$e depletion :one+

W$at is a 9iode;

W$en t$e negati


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W$en t$e positi


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one direction. hen no voltage is applied to the diode, electrons rom the -"type

material %ll holes rom the "type material along the Junction between the layers,

orming a depletion *one. In a depletion *one, the semiconductor material is

returned to its original insulating state "" all o the holes are %lled, so there are no

ree electrons or empty spaces or electrons, and charge can!t (ow.

'o get rid o the depletion *one, you have to get electrons moving rom the -"type

area to the "type area and holes moving in the reverse direction. 'o do this, you

connect the -"type side o the diode to the negative end o a circuit and the "type

side to the positive end. 'he ree electrons in the -"type material are repelled by

the negative electrode and drawn to the positive electrode. 'he holes in the "type

material move the other way. hen the voltage diference between the electrodes

is high enough, the electrons in the depletion *one are boosted out o their holes

and begin moving reely again. 'he depletion *one disappears, and charge moves

across the diode.

I you try to run current the other way, with the "type side connected to thenegative end o the circuit and the -"type side connected to the positive end,

current will not (ow. 'he negative electrons in the -"type material are attracted to

the positive electrode. 'he positive holes in the "type material are attracted to the

negative electrode. -o current (ows across the Junction because the holes and the

electrons are each moving in the wrong direction. 'he depletion *one increases.

6ee How emiconductors orkor more inormation on the entire process.8

'he interaction between electrons and holes in this setup has an interesting side

efect "" it generates light= In the ne#t section, we!ll %nd out e#actly why this is.

How Can a 9iode 0roduce Lig$t;

>ightis a orm o energy that can be released by an atom. It is made up o many

small particle"like packets that have energy and momentum but no mass. 'hese

particles, called photons, are the most basic units o light.

hotons are released as a result o moving electrons. In an atom, electrons move in

orbitals around the nucleus. ;lectrons in diferent orbitals have diferent amounts o

energy. enerally speaking, electrons with greater energy move in orbitals arther

away rom the nucleus.

9or an electron to Jump rom a lower orbital to a higher orbital, something has to

boost its energy level. onversely, an electron releases energy when it drops rom a

higher orbital to a lower one. 'his energy is released in the orm o a photon. A

greater energy drop releases a higher"energy photon, which is characteri*ed by a

higher re+uency. 6heck out How >ight orksor a ull e#planation.8

As we saw in the last section, ree electrons moving across a diode can all into

empty holes rom the "type layer. 'his involves a drop rom the conduction band to
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a lower orbital, so the electrons release energy in the orm o photons. 'his happens

in any diode, but you can only see the photons when the diode is composed o

certain material. 'he atoms in a standard silicon diode, or e#ample, are arranged in

such a way that the electron drops a relatively short distance. As a result, the

photon!s re+uency is so low that it is invisible to the human eye"" it is in the

inrared portion o the light spectrum. 'his isn!t necessarily a bad thing, o course5Inrared >;)s are ideal or remote controls, among other things.

Fisible light"emitting diodes 6F>;)s8, such as the ones that light up numbers in

a digital clock, are made o materials characteri*ed by a wider gap between the

conduction band and the lower orbitals. 'he si*e o the gap determines the

re+uency o the photon "" in other words, it determines the color o the light. hile

>;)s are used in everything rom remote controls to the digital displays on

electronics, visible >;)s are growing in popularity and use thanks to their long

lietimes and miniature si*e. )epending on the materials used in >;)s, they can be

built to shine in inrared, ultraviolet, and all the colors o the visible spectrum in

between.

In the ne#t section we!ll look at the advantages o >;)s.

T$e interior o" a LE9 is actually =uite si#ple, w$ic$ is one o" t$e reasons

t$is tec$nology is so


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in a particular direction. As you can see in the diagram, most o the light rom the

diode bounces of the sides o the bulb, traveling on through the rounded end.

>;)s have several advantages over conventional incandescent lamps. 9or one

thing, they don!t have a %lament that will burn out, so they last much longer.

Additionally, their small plastic bulb makes them a lot more durable. 'hey also %tmore easily into modern electronic circuits.

But the main advantage is e7ciency. In conventional incandescent bulbs, the light"

production process involves generating a lot o heat 6the %lament must be warmed8.

'his is completely wasted energy, unless you!re using the lamp as a heater,

because a huge portion o the available electricity isn!t going toward producing

visible light. >;)s generate very little heat, relatively speaking. A much higher

percentage o the electrical power is going directly to generating light, which cuts

down on the electricity demands considerably.

er"watt, >;)s output more lumens o light than regular incandescent bulbs. >ight

emitting diodes have a higher lu#inous e7cacy6how eMciently electricity is

converted to visible light8 than incandescents "" or e#ample, ewell!s ;vo>u# >;)

bulb produces @.L lumens per watt compared to an incandescent bulb!s 1 lmN

Osource5 ewellP. And they last5 >;)s can have lietimes o >5,555 $ours or

#oreOsource5 )esign 4ecycle IncP.

2p until recently, >;)s were too e#pensive to use or most lighting applications

because they!re built around advanced semiconductor material. 'he price o

semiconductor devices has plummeted since the year 0CCC, however, making >;)s

a more cost"efective lighting option or a wide range o situations. hile they may

be more e#pensive than incandescent lights up ront, their lower cost in the longrun can make them a better buy. everal companies have begun selling >;) light

bulbs designed to compete with incandescent and compact (uorescents that

promise to deliver long lives o bright light and ama*ing energy eMciency.

/ver the ne#t couple o pages we!ll take a look at the uture o >;)s in our homes.

/ne day they may be plugged into our light bulb sockets, lighting up our digital

readouts and illuminating the millions o pi#els that make up our high"de%nition

televisions.

LE9 Lig$t 'ulbs


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1@

around 1,CCC hours, 9>s can last ,CCC hours. 2nortunately, C!Ls contain to?ic

#ercurythat makes them potentially ha*ardous and a pain to dispose o

;nter the >;) light bulb. >;)s ofer the advantages o 9>s "" lower power

consumption and longer lietimes "" without the downside o to#ic mercury. 9or

e#ample, a @C"watt incandescent light bulb draws more than R:CC worth oelectricity per year and provides about CC lumens o lightQ an e+uivalent compact

(uorescent uses less than 17 watts and costs only about R7 o electricity per year.

>;) bulbs are even better, drawing less than watts o power, costing about R:C

per year, and lasting 7C,CCC hours or longer Osource5 )esign 4ecyle IncP. 'here are

only ,@C hours in a whole year "" imagine how long an >;) bulb would last in the

average home=

'hat makes >;)s sound pretty great "" and they are "" but there!s a reason

incandescent and compact (uorescent bulbs are still around. >;) bulbs present a

high up"ront cost compared to other bulbs. Incandescent bulbs sell in packages or

only a ew bucks. As o mid"0C11, ewell!s ;vo>u# >;) bulbs sold or more than RCapiece= However, because o their longer lie spans and dramatically lower power

usage, >;) bulbs make up or the high barrier o entry. ince there!s no to#ic

mercury in an >;), they!re also easier and cheaper to dispose o than 9>s. And

since >;)s can be built to light up in a variety o colors, they don!t need %lters like

other bulbs.

>;) lighting obviously isn!t perect yet. In addition to the high cost barrier, >;)s are

vulnerable to high temperatures. I >;) circuitry gets too hot, more current will pass

through the%unctionmentioned earlier in this article. hen too much current

courses through the Junction, it will cause irreversible burn"out oten called LE9

#eltdown.

>;)s and (uorescents put of ;)s solve both problems.
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Have you ever seen a a gigantic (atscreen 'F barely an inch thickS I you have,

you!ve seen an >;) television. Here!s where the acronyms get a bit conusing5 those

>;) 'Fs are still >) 'Fs, because the screens themselves are comprised o li+uid

crystals. 'echnically, they!re LE9-backlit>) 'Fs. Instead o (uorescent tubes,

>;)s shine light rom behind the screen, illuminating the pi#els to create an image.

)ue to the small si*e and low power consumption o >;)s, >;)"backlit 'Fs are arthinner than regular >) sets and are also more energy eMcient. 'hey can also

provide a wider color gamut, producing more vivid pictures.

Because >;) 'Fs are still in their inancy, several diferent types o >;)"blacklit sets

are on the market "" and not all >;) 'Fs are created e+ual. &any sets use

white LE9 edge lig$tingto shine light across the display. 'he only real advantage

aforded by these sets is thinness. R' LE9-backlit sets, on the other hand,

provide improved color. ome con%gurations even allow or a techni+ue called local

di##ing, where >;)s in diferent parts o the display can be brightened or dimmed

independently to create a more dynamic picture Osource5 >;) 'eleP. And that

highlights one more great advantage o >;)s over compact (uorescent lights5

Because the >;)s can actually be instantly toggled on and of, they produce

awesome black levels in dark scenes. ince the white (uorescent lamps have to

remain on during 'F use, some light tends to bleed through and lighten the picture

in dark scenes.

In the uture, some o the most incredible uses o >;)s will actually come

rom organic light emitting diodes, or LE9s. 'he organic materials used to create

these semiconductors are (e#ible, allowing scientists to create bendable lights and

displays. omeday, />;)s will pave the way or the ne#t generation o 'Fs and

smart phones "" can you imagine rolling your 'F up like a poster and carrying it with

you anywhereS

How 8e#iconductors Work
http://www.ledtele.co.uk/ledvslcd.htmlhttp://electronics.howstuffworks.com/oled.htmhttp://www.ledtele.co.uk/ledvslcd.htmlhttp://electronics.howstuffworks.com/oled.htm


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emiconductors have had a monumental impact on our society. $ou %nd

semiconductors at the heart o microprocessor chipsas well as transistors. Anything

that!s computeri*ed or uses radio wavesdepends on semiconductors.

'oday, most semiconductor chips and transistors are created with silicon. $ou may

have heard e#pressions like


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9oping 8ilicon

$ou can change the behavior o silicon and turn it into a conductor by dopingit. In

doping, you mi# a small amount o an i#purityinto the silicon crystal.

'here are two types o impurities5

)-type" In -"type doping ,phosphorusor arsenicis added to the silicon in small

+uantities. hosphorus and arsenic each have %ve outer electrons, so they!re out o

place when they get into the silicon lattice. 'he %th electron has nothing to bond

to, so it!s ree to move around. It takes only a very small +uantity o the impurity to

create enough ree electrons to allow an electric current to (ow through the silicon.

-"type silicon is a good conductor. ;lectrons have a negative charge, hence the

name -"type.

0-type" In "type doping, boronor galliumis the dopant. Boron and gallium each

have only three outer electrons. hen mi#ed into the silicon lattice, they orm


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0C

A minute amount o either -"type or "type doping turns a silicon crystal rom a

good insulator into a viable 6but not great8 conductor "" hence the name


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01

holes and electrons spring up to take their place. 'he efect is that current

&owsthrough the Junction.

In the ne#t section we!ll look at the uses or diodes and transistors.

9iodes and Transistors

A device that blocks current in one direction while letting current (ow in another

direction is called adiode. )iodes can be used in a number o ways. 9or e#ample, a

device that uses batteries oten contains a diode that protects the device i you

insert the batteries backward. 'he diode simply blocks any current rom leaving the

battery i it is reversed "" this protects the sensitive electronics in the device.

A semiconductor diode!s behavior is not perect, as shown in this graph5

hen re


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A transistoris created by using t$ree layersrather than the two layers used in a

diode. $ou can create either an -- or a - sandwich. A transistor can act as a

switch or an ampli%er.

A transistor looks like two diodes back"to"back. $ou!d imagine that no current could

(ow through a transistor because back"to"back diodes would block current bothways. And this is true. However, when you apply a small current to the center

layero the sandwich, a much larger current can (ow through the sandwich as a

whole. 'his gives a transistor its switc$ingbehavior. A small current can turn a

larger current on and of.

A silicon c$ipis a piece o silicon that can hold thousands o transistors. ith

transistors acting as switches, you can create Boolean gates, and with Boolean

gates you can create microprocessor chips.

'he natural progression rom silicon to doped silicon to transistors to chips is what

has made microprocessors and other electronic devices so ine#pensive and

ubi+uitous in today!s society. 'he undamental principles are surprisingly simple.

'he miracle is the constant re%nement o those principles to the point where, today,

tens o millions o transistors can be ine#pensively ormed onto a single chip.

How Webca#s Work

I you have been e#ploring the ebor any length o time, then you have run across

any number o Webca#sin your travels. ebcams range rom the silly to the

serious "" a ebcam might point at a cofee or a space shuttlelaunch pad. 'here

are business cams, personal cams, private cams, traMc cams... $ou name it and

there!s probably a ebcam pointed at it.
http://computer.howstuffworks.com/boolean.htmhttp://computer.howstuffworks.com/microprocessor.htmhttp://computer.howstuffworks.com/internet/basics/internet-infrastructure.htmhttp://science.howstuffworks.com/space-shuttle.htmhttp://computer.howstuffworks.com/boolean.htmhttp://computer.howstuffworks.com/microprocessor.htmhttp://computer.howstuffworks.com/internet/basics/internet-infrastructure.htmhttp://science.howstuffworks.com/space-shuttle.htm


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Have you ever considered setting up a ebcam yourselS $ou might want to create

a unny ebcam by pointing it at your hamster or putting it inside your rerigerator.

But it turns out there are lots o productive uses or ebcams, too. 9or e#ample5

$ou will be out o town or a week and you want to keep an eye on your

house.

$ou!d like to be able to check on the baby sitter and make sure everything is

/G while you are at work.

$ou!d like to know what your dog does in the back yard all day.

$ou want to let the grandparents watch the new baby during nap time.

I there is something that you would like to monitor remotely, a ebcam makes it

easy.

In this article, we will look at the steps you can take to put up your own simple ebcamera.

T$e 'asic Idea

ebcams, like most things, range rom simple to comple#. I you understand the

essence o a simple ebcam setup, increasing the comple#ity is only a matter o

adding unctionality through sotware, custom code andNor e+uipment connections.

A simple ebcam setup consists o a digital ca#eraattached to your co#puter,

typically through the 2B port. 'he camera part o the ebcam setup is Just a

digital camera "" there!s really nothing special going on there. 'he


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I you don!t have your own eb server, lots o companies ofer you a ree place to

upload your images, saving you the trouble o having to set up and maintain a eb

server or a hosted eb site.

W$at Bou )eed

In order to create a simple ebcam, you need three things5

A ca#erao some sort connected to your computer

A piece o so"twarethat can grab a rame rom the camera periodically

A way to broadcast your i#ages on t$e Web

I you have your own Web ser


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By using this type o service, you avoid having to host andNor maintain your own

eb site. I you are using one o these services and you want the image to reresh

itsel constantly, you need a relatively consistent connection between your

computer and the Internet. I your connection is not consistent, it won!t hurt

anything. It Just means that the image won!t always be up to date.

8etting It *p

In order to e#periment with ebcams and go through the process o setting one up,

got itsel a ebcam. 'o set it up, here is what we did5

1. e went down to the local computer warehouse and bought the Intel ro

Fideo amera.

0. e installed the sotware or the camera on a indows 3 machine.

:. e went to the eb site www.webcam:0.comand downloaded a program

called Webca#D. 'his is a popular sotware package or ebcams. $ou canget a ree demo version or pay R:L.L7 or the ull version. e went ahead

and paid or a registered copy. 6'he complete user!s manual or this product

is available on the eb site. heck it out to see the wide array o eatures

available on today!s ebcam sotware.8

?. e installed ebcam:0. It was a very easy installation.

7. Ater entering the address o the 9' site and a couple o other pieces o

inormation, the ebcam showed its %rst signs o lie=

@. e pointed the camera out the window.

. e then tuned the sotware a bit to reduce the %le si*e o the images and to

enable the te#porary-(le copyingeature.

'here are many diferent eatures you can e#periment with in ebcam:05

streaming video, chat, captions, AFI %les and diferent resolutionsand compression

ratios, to name a ew. ebcam:0 also supports the Autoam eature, which allows

you to create a eb page or your ebcam or ree on the company!s server. 'he

sotware makes it simple.

As you can see, setting up a basic ebcam is e#tremely easy. I nothing else, the

setup described here is a un, ine#pensive and simple way to e#periment with a

ebcam and see what you can do with one o your own=

Ad


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otion sensing" 'he ebcam takes a new picture when it detects motion.

I#age arc$i


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o the house, or outsideS In that case, you need to purchase a camera with e#ternal

connections. $ou have a ew options5

$ou can place a standard camera anywhere in the house and run a video

cable with 4A Jacks on it rom the camera to the computer. 'here are all

sorts o places on the eb that sell small pinhole video cameras, either ontheir own or embedded in things like clocks and smoke detectors. $ou can

%nd small security cameras or less than R1CC. avoid the cable by using

a radio, an ;thernetconnection or a i"9isetup. I you already have a home

network, connecting an e#ternal ebcam to your computer probably won!t

re+uire any additional networking.

&onitoring your home and sharing images via the eb are only a couple o the

things you can do with your ebcam. 'here are any number o ways to make use o

a camera that!s connected to your computer. $ou can get sotware that will let you

make video phone callswith a riend who also has a ebcam. $ou can hold a video"

conerencing session with business associates on the other side o the world. $oucan conduct a video interview and broadcast it live on your blog. ome ebcam

sotware will even deliver images directly to your eb"enabled )Aor smartphone.

/ther products let you connect your camcorder to your ebcam setup so you can

let everybody watch your vacation ootage via the Internet. 'he possibilities are

endless.

How Ato#s Work
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It has been said that during the 0Cth century, man harnessed the power o the

atom. e made atomic bombsand generated electricityby nuclear power. e even

split the atom into smaller pieces called subato#ic particles.

But what e#actly is an atomS hat is it made oS hat does it look likeS 'he pursuit

o the structure o the atom has married many areas o chemistry and physics in

perhaps one o the greatest contributions o modern science. In this article, we will

ollow this ascinating story o how discoveries in various %elds o science resulted

in our modern view o the atom. e will look at the conse+uences o knowing theatom!s structure and how this structure will lead to new technologies.
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In a silicon lattice, all silicon ato#s bond per"ectly to "our neig$bors,

lea


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entitled


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or hydrogen pero#ide8. o, he could not say anything about the numbers o each

atom in the molecules o speci%c substances. )id water have one o#ygen with one

hydrogen or one o#ygen with two hydrogensS 'his point was resolved when

chemists %gured out how to weigh atoms.

8i#plest #odel o" an ato#

How uc$ 9o Ato#s Weig$;

'he ability to weigh atoms came about by an observation rom an Italian chemist

named A#adeo A


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newly discovered atomic masses in cards. He arranged the elements by increasing

atomic mass and noticed that elements with similar properties appeared at regular

intervals or periods. &endeleev!s table had two problems5

'here were some gaps in his


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::

He ound that i the tube was placed within an electric or magnetic %eld, then

the cat$ode rays could be de&ected or #o


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Rut$er"ordMs


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the weight o the nucleus. 'hereore, a third, neutrally charged particle must e#ist=

It wasa#es C$adwick, a British physicist and co"worker o 4utherord, who

discovered the third subatomic particle, the neutron. hadwick bombarded

beryllium oil with alpha particles and noticed a neutral radiation coming out. 'his

neutral radiation could in turn knock protons out o the nuclei o other substances.

hadwick concluded that this radiation was a stream o neutrally charged particleswith about the same mass as a protonQ the neutron has a mass o 1.@7 # 1C "

0?grams.

-ow that the parts o the atom were known, how were they arranged to make an

atomS 4utherord!s gold oil e#periment indicated that the nucleus was in the center

o the atom and that the atom was mostly empty space. o, he envisioned the atom

as the positively charged nucleus in the center with the negatively charged

electrons circling around it much like a planet with moons. Although he had no

evidence that the electrons circled the nucleus, his model seemed reasonableQ

however, it presented a problem. As the electrons moved in a circle, they would lose

energy and give of light. 'he loss o energy would slow the electrons down. >ike

any satellite, the slowing electrons would all into the nucleus. In act, it was

calculated that a 4utherord atom would last only billionths o a second beore

collapsing= omething was missing=

W$ite lig$t passing t$roug$ a pris#+

uantu# ec$anics6 0utting It All Toget$er

At the same time that discoveries were being made with radioactivity, physicists

and chemists were studying how lightinteracted with matter. 'hese studies began

the %eld o=uantu# #ec$anicsand helped solve the structure o the atom.

uantu# ec$anics 8$eds Lig$t on t$e Ato#6 T$e 'o$r odel

hysicists and chemists studied the nature o the lightthat was given of when

electric currents were passed through tubes containing gaseous elements

6hydrogen, helium, neon8 and when elements were heated 6e.g., sodium, potassium,

calcium, etc.8 in a (ame. 'hey passed the light rom these sources through a

spectrometer 6a device containing a narrow slit and a glass prism8.
http://science.howstuffworks.com/satellite.htmhttp://science.howstuffworks.com/light.htmhttp://science.howstuffworks.com/light.htmhttp://science.howstuffworks.com/satellite.htmhttp://science.howstuffworks.com/light.htmhttp://science.howstuffworks.com/light.htm


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:@

Continuous spectru# o" w$ite lig$t+

hoto courtesy -AA

-ow, when you pass sunlight through a prism, you get a continuous spectrum o

colors like a rainbow. However, when light rom these various sources was passed

through a prism, they ound a dark background with discrete lines.

Hydrogen spectru#

hoto courtesy -AA

Heliu# spectru#

hoto courtesy -AA

;ach element had a uni+ue spectrum and the wavelengtho each line within a

spectrum had a speci%c energy 6see How >ight orksor details on the relationship

between wavelength and energy8.

In 1L1:, a )anish physicist named )iels 'o$rput 4utherord!s %ndings together

with the observed spectra to come up with a new model o the atom in a real leap ointuition. Bohr suggested that the electrons orbiting an atom could only e#ist at

certain energy levels 6i.e., distances8 rom the nucleus, not at continuous levels as

might be e#pected rom 4utherord!s model. hen atoms in the gas tubes absorbed

the energy rom the electric current, the electrons became e#cited and Jumped rom

low energy levels 6close to the nucleus8 to high energy levels 6arther out rom the

nucleus8. 'he e#cited electrons would all back to their original levels and emit

energy as light. Because there were speci%c diferences between the energy levels,

only speci%c wavelengths o light were seen in the spectrum 6i.e., lines8.
http://science.howstuffworks.com/light.htmhttp://science.howstuffworks.com/light.htmhttp://science.howstuffworks.com/light.htmhttp://science.howstuffworks.com/light.htm


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'o$r #odels o"


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:

Bohr!s model was the predominant model until new discoveries in +uantum

mechanics were made.

*A)T* ECHA)IC8

Branch o physics that deals with the motion o particles by their wave properties at

the atomic and subatomic level.

Electrons Can 'e$a


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'he absorbed energy will change the electron!s position.

e can never know both the #o#entu# and positiono an electron in an atom.

'hereore, Heisenberg said that we shouldn!t view electrons as moving in well"

de%ned orbits about the nucleus=

ith de Broglie!s hypothesis and Heisenberg!s uncertainty principle in mind, an

Austrian physicist namedErwin 8c$rodingerderived a set o e+uations or wa


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?C

It was later suggested that no two electrons could be in the e#act same state, so a

ourth +uantum number was added. 'his number was related to the direction that

the electron spins while it is moving in its orbit 6i.e., clockwise, and

counterclockwise8. /nly two electrons could share the same orbital, one spinning

clockwise and the other spinning counterclockwise.

'he orbitals had diferent shapes and ma#imum numbers at any level5

s6sharp8 " spherical 6ma# E 18

p6principal8 " dumb"bell shaped 6ma# E :8

d6difuse8 " our"lobe"shaped 6ma# E 78

"6undamental8 " si#"lobe shaped 6ma# E 8

'he names o the orbitalWs came rom names o atomic spectral eatures beore

+uantum mechanics was ormally invented. ;ach orbital can hold only twoelectrons. Also, the orbitalWs have a speci%c order o %lling, generally5

However, there is some overlap 6any chemistry te#tbook has the details8.

'he resulting model o the atom is called the =uantu# #odelo the atom.

odium has 11 electrons distributed in the ollowing energy levels5

1. one s orbital" two electrons

0. one s orbital" two electrons and t$ree p orbitals6two electrons each8

:. one s orbital" one electron

4ight now, the +uantum model is the most realistic vision o the overall structure o

the atom. It e#plains much o what we know about chemistry and physics. Here are

some e#amples5


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T$e #odern periodic table o" t$e ele#ents ele#ents are ordered based

on ato#ic nu#ber rat$er t$an #ass2+

hemistry5'he eriodic 'able" the 'able!s pattern and arrangement re(ects

the arrangement o electrons in the atom. ;lements have diferent atomic

numbers " the number o protons or electrons increases up the table as

electrons %ll the shells. ;lements have diferent atomic masses " the number

o protons plus neutrons increases up the table. 4ows " elements o each row

have the same number o energy levels 6shells8. olumns " elements havethe same number o electrons in the outermost energy level or shell 6one to

eight8. C$e#ical reactions" e#change o electrons between various atoms

6giving, taking, or sharing8. ;#change involves electrons in the outermost

energy level in attempts to %ll the outermost shell 6i.e., most stable orm o

the atom8.

hysics Radioacti


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?0

8T i#age O n# ? O n#2 o" a single :ig:ag c$ain o" cesiu# ato#s red2 on

a galliu#-arsenside sur"ace blue2

Can We 8ee Ato#s;

Atoms are so small that we cannot see them with our eyes 6i.e., microscopic8. 'ogive you a eel or some si*es, these are appro#imate diameters o various atoms

and particles5

atom E 1 # 1C"1Cmeters

nucleus E 1 # 1C"17to 1 # 1C "1?meters

neutron or proton E 1 # 1C"17meters

electron " not known e#actly, but thought to be on the order o 1 # 1C"

1meters

$ou cannot see an atom with a light microscope. However, in 1L1, a type o

microscope called a scanning tunneling #icroscope 8T2was developed. 'he

'& consists o the ollowing5

A very small, sharp tip that conducts electricity 6probe8

A rapid pie*oelectricscanning device to which the tip is mounted

;lectronic components to supply current to the tip, control the scanner and

accept the signals rom the motion sensor

omputer to control the system and do data analysis 6data collection,

processing, display8

'he '& works like this5

A current is supplied to the tip 6probe8 while the scanner rapidly moves the

tip across the surace o a conducting sample.
http://science.howstuffworks.com/light-microscope.htmhttp://science.howstuffworks.com/quartz-watch1.htmhttp://science.howstuffworks.com/light-microscope.htmhttp://science.howstuffworks.com/quartz-watch1.htm


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hen the tip encounters an atom, the (ow o electrons between the atom

and the tip changes.

'he computer registers the change in current with the #,y"position o the

atom.

'he scanner continues to position the tip over each #,y"point on the sample

surace, registering a current or each point.

'he computer collects the data and plots a map o current over the surace

that corresponds to a map o the atomic positions.

'he process is much like an old phonograph where the needle is the tip and the

grooves in the vinyl record are the atoms. 'he '& tip moves over the atomic

contour o the surace, using tunnelingcurrent as a sensitive detector o atomic

position.

'he '& and new variations o this microscope allow us to see atoms. In addition,the '& can be used to manipulate atoms as shown here5

Ato#s can be positioned on a sur"ace using t$e 8T tip, creating a custo#

pattern on t$e sur"ace+

In summary, science in the 0Cth century has revealed the structure o the atom.

cientists are now conducting e#periments to reveal details o the structure o the

nucleus and the orces that hold it together.


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How Radio Works by nafees