phy presentation

7/28/2019 Phy Presentation

1/25


2/25


3/25

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.


4/25

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.


5/25


6/25


7/25


8/25

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


9/25


10/25


11/25

FORM OF CAPACITOR


12/25

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


13/25

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


14/25

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


15/25

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


16/25

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


17/25

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


18/25

Similar to Mica Capacitors But, stability and frequency

characteristics are better Ultra-reliable, ultra-stable, and

resistant to nuclear radiation.But high cost.


19/25

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)


20/25

No polarity

used in filter circuits or timingapplications


21/25


22/25


23/25

THECHARGEOF 1 COULOMBSTOREDONEACH

OFTHECONDUCTINGPLATESASARESULTOFAPOTENTIALDIFFERENCE

OF 1 VOLTBETWEENTHETWOPLATES


24/25

Parallel-plate capacitor

separated by a vacuum

Parallel-platecapacitor separatedby a dielectric

material


25/25

Parallel Series

phy presentation

Documents