Electronic Devices – Capacitor

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

C=Ԑ _o Ԑ_r A / d farad A=area of each plate in m²,

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

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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.

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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

Image Source

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General Classification

• Filter type
• Storage type

Capacitor Type

• Fixed type
• Variable type

Fixed type

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

Variable type

variable type also called “gung”

• Ceramic variable type
• Plastic variable type
• Glass variable type
• Air variable type

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Uses

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

Applications

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

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

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Reference

• http://www.robotoid.com
• http://www.sphere.bc.ca/test/production-parts/avx-rad-cer-thomson.pdf
• http://www.ee.ryerson.ca:8080/~jkoch/prototype/cap.html
• https://learn.sparkfun.com/tutorials/capacitors
• https://www.youtube.com/watch?v=sW0a9d_vWoc

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