Electronic Devices – Capacitor


A capacitor consists of two conducting plates separated by an insulating medium. The capacitor can store electric charges, in the form of voltage in electric field. The capacitor blocks direct current. The capacitor opposes any sudden change of voltage applied to it. Capacitor only allows the Alternating current. Capacitor makes the time delay

C=Ԑ o Ԑr A / d farad A=area of each plate in m2,

  • d=distance between the plates in meter, Ԑr =relative dielectric constant(permittivity).
  • Ԑ o=dielectric constant(permittivity)of free space,

Michael Faraday (1791 – 1867)

A great experimentalism and popularize of science. He is most famous for his work on magnetic induction, but also did fundamental work related to electrolysis He worked at the Royal Institution (one of the first scientific research institutes) and established the Christmas Lectures on science for young people which are still running.



Capacitor Unit Relationship Chart

Prefix Name Abbreviation Weight Equivalent Farads

  • Picofarad pF 10^-12 = 0.000000000001 F
  • Nanofarad nF 10^-9 = 0.000000001 F
  • Microfarad µF 10^-6 = 0.000001 F
  • Milifarad mF 10^-3 = 0.001 F
  • Kilofarad kF 10^3 = 1000 F

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Capacitor General Classification

  • Filter capacitor
  • Storage capacitor

Capacitor Type of Capacitor

  • Fixed capacitor
  • Variable capacitor

Fixed Capacitor

  • Electrolytic capacitors.
    • Polarized electrolytic capacitor
      • Aluminium type
      • Tantalum type
    • Non polarized electrolytic capacitor
  • Non-electrolytic capacitors. (it has no polarity & colour coding)
    • Ceramic capacitor
      • Disc capacitor
      • Tubular capacitor
      • Monolithic capacitor
      • Barrier level capacitor
    • Plastic capacitor
      • Polystyre capacitor
      • Polyster capacitor
      • Polycarbonate capacitor
    • Mica capacitor
      • Stacked mica capacitor
      • Silvered mica capacitor
    • Paper capacitor
      • Impregnated paper capacitor
      • Metalized paper capacitor

Variable Capacitor

variable capacitor also called “gung”

  • Ceramic variable capacitor
  • Plastic variable capacitor
  • Glass variable capacitor
  • Air variable capacitor


Capacitor use

  • electrolytic capacitors: used as filter in a power supply, time constant circuits, bypass, coupling/decoupling, smoothing and power electronics application.
  • Non polarized electrolytic capacitor: used in applications such as AC motor starting, cross over networks and large pulse signals.
  • Ceramic capacitor: used as bypass capacitor and used in decoupling applications, frequency discriminators and biasing applications.
  • Tubular capacitor: used as isolate the antennas in receiver
  • Polystyrene capacitor: used in coupling, resonant and measuring circuits.
  • Polyester capacitor: used for coupling/decoupling applications, and also in power electronics.
  • Poly carbonate capacitor: used in dc application.
  • Mica capacitor: used as coupling capacitors at high frequency, in radio transmitters, measuring circuits, bypass circuits and RF resonant circuits
  • VARIABLE CAPACITOR- (variable capacitor also called “gung”) used in tuning circuits of communication receivers, transmitters and in oscillator.


  1. Every circuit has must have the capacitor in the first stage.
  2. Capacitor makes the continuous current flow in the circuit.
  3. Variable capacitors are used in frequency turning in TV application.

*after shutdown the power the capacitor stores the electric signal and it gives to the micro controller





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