7/26/2019 Articol Despre Condensatori

1/4

History of the Capacitor

The invention of the capacitor varies somewhat depending on who you ask. There are records that

indicate a German scientist named Ewald Georg von Kleist invented the capacitor in November 17!.

"everal months later #ieter van $usschenbroek% a &utch professor at the 'niversity of (eyden came

up with a very similar device in the form of the Leyden jar% which is typically credited as the first

capacitor. "ince Kleist didn)t have detailed records and notes% nor the notoriety of his &utch

counterpart% he)s often overlooked as a contributor to the capacitor)s evolution. *owever% over the

years% both have been given e+ual credit as it was established that their research was independent of

each other and merely a scientific coincidence ,source- illiams/.

The (eyden 0ar was a very simple device. t consisted of a glass 0ar% half filled with water and lined

inside and out with metal foil. The glass acted as the dielectric% although it was thought for a time that

water was the key ingredient. There was usually a metal wire or chain driven through a corkin the top

of the 0ar. The chain was then hooked to something that would deliver a charge% most likely a hand2

cranked staticgenerator.3nce delivered% the 0ar would hold two e+ual but opposite charges in

e+uilibrium until they were connected with a wire% producing a slight spark or shock ,source- illiams/.

4en0amin 5ranklin worked with the (eyden 0ar in his e6periments with electricity and soon found that a

flat piece of glass worked as well as the 0ar model% prompting him to develop the flat capacitor% or

5ranklin s+uare. ears later% English chemist $ichael 5araday would pioneer the first practical

applications for the capacitor in trying to store unusedelectronsfrom his e6periments. This led to the

first usable capacitor% made from large oilbarrels. 5araday)s progress with capacitors is what

eventually enabled us to deliver electric power over great distances. 8s a result of 5araday)s

achievements in the field of electricity% the unit of measurement for capacitors% or capacitance%

became known as the farad ,source- 9amasamy/.

n a way% a capacitor is a little like a battery. 8lthough they work in completely different ways%

capacitors and batteries both store electrical energy. f you have read *ow 4atteries ork%then you

know that a battery has two terminals. nside the battery% chemical reactions produceelectronson one

terminal and absorb electrons on the other terminal. 8 capacitor is much simpler than a battery% as it

can)t produce new electrons 22 it only stores them.

n this article% we)ll learn e6actly what a capacitor is% what it does and how it)s used in electronics. e)ll

also look at the history of the capacitor and how several people helped shape its progress.

nside the capacitor% the terminals connect to two metal platesseparated by a non-conducting

substance,or dielectric. ou can easily make a capacitor from two pieces ofaluminumfoil and a

piece of paper. t won)t be a particularly good capacitor in terms of its storage capacity% but it will work.

n theory% the dielectric can be any non2conductive substance. *owever% for practical applications%

specific materials are used that best suit the capacitor)s function. $ica% ceramic% cellulose% porcelain%

$ylar% Teflonand evenairare some of the non2conductive materials used. The dielectric dictates what

kind of capacitor it is and for what it is best suited. &epending on the si:e and type of dielectric% some

capacitors are better for high fre+uency uses% while some are better for high voltage applications.

;apacitors can be manufactured to serve any purpose% from the smallest plastic capacitor in your

calculator% to an ultra capacitor that can power a commuter bus. N8"8uses glass capacitors to help

http://electronics.howstuffworks.com/capacitor3.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://home.howstuffworks.com/question550.htmhttp://home.howstuffworks.com/question550.htmhttp://electronics.howstuffworks.com/gadgets/travel/hand-powered-generators.htmhttp://electronics.howstuffworks.com/gadgets/travel/hand-powered-generators.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://science.howstuffworks.com/electron-info.htmhttp://science.howstuffworks.com/electron-info.htmhttp://science.howstuffworks.com/environmental/energy/oil-drilling.htmhttp://science.howstuffworks.com/environmental/energy/oil-drilling.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://science.howstuffworks.com/electron-info.htmhttp://science.howstuffworks.com/electron-info.htmhttp://electronics.howstuffworks.com/http://science.howstuffworks.com/aluminum.htmhttp://science.howstuffworks.com/aluminum.htmhttp://entertainment.howstuffworks.com/artshttp://entertainment.howstuffworks.com/artshttp://science.howstuffworks.com/air-info.htmhttp://science.howstuffworks.com/air-info.htmhttp://science.howstuffworks.com/nasa.htmhttp://home.howstuffworks.com/question550.htmhttp://electronics.howstuffworks.com/gadgets/travel/hand-powered-generators.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://science.howstuffworks.com/electron-info.htmhttp://science.howstuffworks.com/environmental/energy/oil-drilling.htmhttp://electronics.howstuffworks.com/capacitor3.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://science.howstuffworks.com/electron-info.htmhttp://electronics.howstuffworks.com/http://science.howstuffworks.com/aluminum.htmhttp://entertainment.howstuffworks.com/artshttp://entertainment.howstuffworks.com/artshttp://science.howstuffworks.com/air-info.htmhttp://science.howstuffworks.com/nasa.htmhttp://electronics.howstuffworks.com/capacitor3.htm

7/26/2019 Articol Despre Condensatori

2/4

wake up the space shuttle)s circuitry and help deploy space probes. *ere are some of the various

types of capacitors and how they are used.

8ir 2 3ften used in radio tuning circuits

$ylar 2 $ost commonly used for timer circuits likeclocks%alarms and counters

Glass2 Good for high voltage applications

;eramic 2 'sed for high fre+uency purposes like antennas%

7/26/2019 Articol Despre Condensatori

3/4

*ere you have a battery% a light bulband a capacitor. f the capacitor is pretty big% what you will notice

is that% when you connect the battery% the light bulb will light up as current flows from the batteryto the

capacitor to charge it up. The bulb will get progressively dimmer and finally go out once the capacitor

reaches its capacity. f you then remove the battery and replace it with a wire% current will flow from

one plate of the capacitor to the other. The bulb will light initially and then dim as the capacitor

discharges% until it is completely out.

n the ne6t section% we)ll learn more about capacitance and take a detailed look at the different ways

that capacitors are used.

LIKE A WATE T!WE

3ne way to visuali:e the action of a capacitor is to imagine it as awater towerhooked to a pipe. 8

water tower ?stores? water pressure 22 when the water system pumps produce more water than a town

needs% the e6cess is stored in the water tower. Then% at times of high demand% the e6cess water flows

out of the tower to keep the pressure up. 8 capacitor stores electrons in the same way and can then

release them later.

"arad

8 capacitor)s storage potential% orcapacitance% is measured in units called farads. 8 12farad capacitor

can store one coulomb =coo2lomb> of charge at 1 volt. 8 coulomb is A.B!e1C =A.B! D 1F1C% or A.B!

billion billion> electrons.3ne a#prepresents a rate of electron flow of 1 coulomb of electrons per

second% so a 12farad capacitor can hold 1 amp2second of electrons at 1 volt.

8 12farad capacitor would typically be pretty big. t might be as big as a can of tuna or a 12liter soda

bottle% depending on the voltage it can handle. 5or this reason% capacitors are typically measured in

microfarads =millionths of a farad>.

To get some perspective on how big a farad is% think about this-

http://home.howstuffworks.com/light-bulb.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://people.howstuffworks.com/water.htmhttp://people.howstuffworks.com/water.htmhttp://people.howstuffworks.com/water.htmhttp://science.howstuffworks.com/electron-info.htmhttp://science.howstuffworks.com/electron-info.htmhttp://home.howstuffworks.com/light-bulb.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://people.howstuffworks.com/water.htmhttp://science.howstuffworks.com/electron-info.htm

7/26/2019 Articol Despre Condensatori

4/4

8 standard alkaline 88 batteryholds about B.C amp2hours.

That means that a 88 battery can produce B.C amps for an hour at 1.! volts =about .B watt2

hours 22 a 88 battery can light a 2watt bulb for a little more than an hour>.

(et)s call it 1 volt to make the math easier. To store one 88 battery)s energy in a capacitor% you

would need %A D B.C H 1%C farads to hold it% because an amp2hour is %A amp2seconds.

f it takes something the si:e of a can of tuna to hold a farad% then 1%C farads is going to take up a

(3T more space than a single 88 battery@ 3bviously% it)s impractical to use capacitors to store any

significant amount of power unless you do it at a high voltage.Applications

The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a

tiny fraction of a second% where a battery would take minutes to completely discharge. That)s why the

electronic flash on acamerauses a capacitor 22 the battery charges up the flash)s capacitor over

several seconds% and then the capacitor dumps the full charge into the flash tube almost instantly. This

can make a large% charged capacitor e6tremely dangerous 22 flash units and TIshave warnings about

opening them up for this reason. They contain big capacitors that can% potentially% kill you with the

charge they contain.

;apacitors are used in several different ways in electronic circuits-

"ometimes% capacitors are used to store charge for high2speed use. That)s what a flash does.

4ig lasersuse this techni+ue as well to get very bright% instantaneous flashes.

;apacitors can also eliminate ripples. f a line carrying &; voltage has ripples or spikes in it% a

big capacitor can even out the voltage by absorbing the peaks and filling in the valleys.

8 capacitor can block &; voltage. f you hook a small capacitor to a battery% then no currentwill flow between the poles of the battery once the capacitor charges. *owever% any alternating current

=8;> signal flows through a capacitor unimpeded. That)s because the capacitor will charge and

discharge as the alternating current fluctuates% making it appear that the alternating current is flowing.

n the ne6t section% we)ll look at the history of the capacitor and how some of the most brilliant minds

contributed to its progress.

CA$ACITI%E T!&CH 'CEE('

3ne of the more futuristic applications of capacitors is the capacitive touch screen. These are glass

screens that have a very thin% transparent metallic coating. 8 built2in electrode pattern charges the

screen so when touched% a current is drawn to the finger and creates a voltage drop. This e6act

location of the voltage drop is picked up by a controller and transmitted to a computer. These touch

screens are commonly found in interactive building directories and more recently in 8pple)s i#hone.

http://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://electronics.howstuffworks.com/camera.htmhttp://electronics.howstuffworks.com/camera.htmhttp://electronics.howstuffworks.com/tv.htmhttp://science.howstuffworks.com/laser.htmhttp://computer.howstuffworks.com/question716.htmhttp://computer.howstuffworks.com/http://electronics.howstuffworks.com/iphone.htmhttp://electronics.howstuffworks.com/iphone.htmhttp://electronics.howstuffworks.com/everyday-tech/battery.htmhttp://electronics.howstuffworks.com/camera.htmhttp://electronics.howstuffworks.com/tv.htmhttp://science.howstuffworks.com/laser.htmhttp://computer.howstuffworks.com/question716.htmhttp://computer.howstuffworks.com/http://electronics.howstuffworks.com/iphone.htm