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German scientist named Ewald Georg von Kleistinvented the capacitor in November 1745. Several
months laterPieter van Musschenbroek, a Dutchprofessor at the University of Leyden came up witha very similar device in the form of the Leyden jar,which is typically credited as the first capacitor.
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1. consisted of a glass jar, half filled with
waterand lined inside and out withmetal foil.2. The glass acted as the dielectric,
although it was thought for a time thatwaterwas the key ingredient.
3. There was usually a metal wire orchain
driven through a cork in the top of thejar.
4. The chain was then hooked tosomething that would deliver a charge,most likely a hand-cranked staticgenerator.
5. Once delivered, the jar would hold twoequal but opposite charges inequilibrium until they were connectedwith a wire, producing a slight spark orshock.
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Application Suitable types with reasons details & commentsPower supply smoothing Aluminium electrolytic High capacity andhigh ripple current capability **Audio frequency coupling Aluminium Electrolytic: High capacitance
Tantalum: High capacitance and small
size
Polyester / polycarbonate : Cheap, but
values not as high as those available with
electrolyticRF coupling
Ceramic COG: Small, cheap and low loss
Ceramic X7R: Small and cheap but
higher loss than COG, although high
capacitance per volume
Polystyrene: Very low loss, but larger and
more expensive than ceramicRF decoupling Ceramic COG: Small, low loss, but valueslimited to around 1000 pF max.
Ceramic X7R: Small, low loss, higher
values available than for COG typesTuned circuits
Silver mica: Close tolerance, low loss andstable, but high cost
Ceramic COG: Close tolerance low loss
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FORM OF CAPACITOR
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constructed with materialssuch as titanium acidbarium for dielectric
use in high frequencyapplications
used to by-pass highfrequency signals to ground
very small capacitancevalues and very small sizes
very small size and value,very cheap, reliable
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Used thin polyester film as thedielectric
not high tolerance cheap and handy. No polarity,
mainly used when a highertolerance is needed thenpolyester caps can offer
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Use thin polyester film as a dielectric Not as high a tolerance as
polypropylene Cheap and handy, temperature stable,
readily available, widely used. Temperature stability is poorer than
paper capacitors
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Made of Tantalum Pentoxide electrolytic capacitors but used
with a material called tantalum
for the electrodes Tantalum capacitors are a little
bit more expensive thanaluminum electrolytic capacitors
Used for circuits which demandhigh stability in the capacitancevalues
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Used in certain high voltageapplications
Mostly been replaced by plasticfilm capacitors
paper is highly hygroscopic,absorbing moisture from theatmosphere despite plasticenclosures
Absorbed moisture degradesperformance by increasing
dielectric losses (power factor)and decreasing insulationresistance
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used as a dielectric Used in resonance circuits, frequency
filters, and military RF applications. Highly stable, good temperature
coefficient, excellent for endurancebecause of their frequencycharacteristics, no large values, highvoltage types available, can beexpensive but worth the extra dimes
It does not change physically orchemically with age
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Similar to Mica Capacitors But, stability and frequency
characteristics are better Ultra-reliable, ultra-stable, and
resistant to nuclear radiation.But high cost.
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Made of electrolyte, basicallyconductive salt in solvent
Aluminium electrodes are usedby using a thin oxidationmembrane
common type, polarizedcapacitor Used in Ripple filters, timing
circuits Cheap, readily available, good
for storage of charge (energy)
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No polarity
used in filter circuits or timingapplications
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THECHARGEOF 1 COULOMBSTOREDONEACH
OFTHECONDUCTINGPLATESASARESULTOFAPOTENTIALDIFFERENCE
OF 1 VOLTBETWEENTHETWOPLATES
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Parallel-plate capacitor
separated by a vacuum
Parallel-platecapacitor separatedby a dielectric
material
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Parallel Series