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CAPACITORS

CAPACITORS. OBJECTIVES. Proper understanding of the definition of capacitors . Identify the relationship between a resistor and a capacitor. Calculate capacitance in series and parallel circuit and in terms of same capacitance value .

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CAPACITORS

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  1. CAPACITORS

  2. OBJECTIVES Properunderstanding of thedefinition of capacitors. Identifytherelationshipbetween a resistor and a capacitor. Calculatecapacitance in series and parallelcircuit and in terms of samecapacitancevalue. Classifycapacitorsaccordingtomaterials and usage. Relate thetopictoeveryday living.

  3. CAPACITOR A capacitoris a devicethatstoreselectrons. Thebasic capacitor ismade up of twoconductorsseparatedbyaninsulator, ordielectric. Dependingonhowthe capacitor isbuilt, thedielectric can bemade of paper, plastic, mica, ceramic, glass, a vacuumoranyothersuch non conductive material.

  4. UNIT OF MEASUREMENT Capacitor electronstoringability (itscapacitance) ismeasured in Farads. 1 Faradisactually a hugenumber of electrons (6, 280, 000, 000, 000, 000, 000 electronstobeexact), so weusuallyratecapacitors in microfarads (µF) and picofarads (pF).

  5. 1 µF isequalto 0.000001 F 1 pFisequalto 0.000000000001 F

  6. Capacitors comes in a variety of sizes, shapes, models, orifyou so desirethey can bemanufacturedbyyourspecifications.

  7. MATERIALS Capacitorsalso come in a variety of materials, toname a few : Aluminumfoil, Polypropylene, Polyester (Mylar), Polyesterene, Polycarbonate, KraftPaper, Mica, Teflon, Epoxy, Oil-filled, Electrolyte, Tantalum, and thelistgoeson. Latestproduct (in reseach) isNobium.

  8. Thevalue of a capacitor can varyfrom a fraction of a picofaradto more than a million µF (µ means ´micro´). Voltagelevels can rangefrom a coupleto a substantialcouplehundredthousand volts.

  9. CHARACTERISTICS It can storeelectricchargeeventhoughthevoltagesourceisalreadydisconnected. It can dischargeelectricalvoltages.

  10. SCHEMATIC SYMBOLS

  11. TYPES Anearlyclassificationissettledforcapacitors. Thesewerestablished and categorizedintofournamely (a)non-polarized , (b)polarized, (c) variable, and (d) trimmer.

  12. Non-Polarized Capacitor Non-polar capacitor is a type of capacitor that can beconnectedanyway in a circuit. In otherwords, thereis no positive ornegative. Commontypes of non-polar capacitors are ceramic,mica and someelectrolytic.

  13. There are twotypes of non-polarizedcapacitors. Theplasticfoilthat are non polarizedbynatureand electrolytic non polarizedcapacitorsthat are actuallytwocapacitorsin series (back to back) so thattheresultis non polarizedwithhalfthecapacitance.

  14. PolarizedCapacitors A capacitor storeselectriccharge. Thistypemustbeconnectedthecorrectwayaround. A capacitor storeselectriccharge. A capacitor isusedwith a resistor in a timingcircuit. It can alsobeused as a filter, to block DC signalsbutpass AC signals.

  15. Polarizedcapacitors are theelectrolytictypeortandaliumtype. Theyhavelargeleakagecurrentifthevoltageisinverted. They are cheaperthanequivalent non-polarizedcapacitors. They are sometimesphysicallysmallerthat non-polarizedequivalents. They are meantfor AC signalsrespectively.

  16. Electrolyticcapacitorshave a polarityunlikeothercapacitors. Thisisduetothefactthataluminum oxide layerisheld in place bytheelectricfield, and when reverse-biased, itdissolvesintotheelectrolyte. Thisallowsa short circuitbetweentheelectrolyte and thealuminum.

  17. NON-POLARIZED vs. POLARIZED Non-polarized capacitor has a bigsizewiththesmallercapacitance, and isusedboth in DC or AC circuits, loworhighfrequencies. Polarized capacitor has a smallsizewiththelargecapacitance, and isusedonly in DC circuitsorcircuitsrelatedto DC current.

  18. NON-POLARIZED vs. POLARIZED Non-polarized capacitor has a verysmallleakagecurrent, highfrequency response of up tohundreds of GHz up totypes. Polarized capacitor has a largeleakagecurrentlowfrequency response of only up toabouttens of kHz at aluminumor 1MHz at tantalium caps.

  19. NON-POLARIZED vs. POLARIZED In general, theycannotreplaceeachother!!!

  20. VARIABLE CAPACITORS A variable capacitor is a capacitor whosecapacitance can bevaried. These are usuallymade up of oneor more movingplates and oneor more non movingplatesseparatedbythedielectric. Bymovingtheplates, we can varythecapacitance. A variable capacitor isused in a radio tuner.

  21. TRIMMER CAPACITORS Thistype of variable capacitor (trimmer) isoperatedwith a smallscrewdriveror similar tool. Itisdesignedtobe set whenthecircuitismade and thenleftwithoutfurtheradjustment.

  22. EXAMPLES FIXED / NORMAL /NON-POLARIZED Ceramiccapacitors – dipguard, monolithic (axial leads), monolithic (radial leads), disc, surfacemount Film capacitors – polyester (axial leads), polyester (radial leads), polypropylene (axial leads), polypropylene (radial leads), polystyrene (axial leads)

  23. EXAMPLES POLARIZED CAPACITORS AluminumElectrolyticcapacitors – axial leads, radial leads, computer grade, snapmount, twist lock, surfacemount Tantalumcapacitors – solidtantalum (axial leads), solidtantalum (radial leads), foiltantalum (axial leads),foiltantalum (radial leads), dippedtantalum, wettantalum, surfacemount

  24. EXAMPLES VARIABLE CAPACITORS Semiconductor diodes – rectifier, zener, LED Bipolar Junction Transistors (BJT) – PNP, NPN IntegratedCircuit

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