energy store in dielectric

Discussion in 'General Electronics Chat' started by TAKYMOUNIR, Mar 5, 2013.

  1. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
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    1
    in the capacitor the energy store in dielectric and also in transformer the energy store in the gap(dielectric) so my question is how the dielectric store the energy and the conductor can not store energy?
    second question how the chemical capacitor charge only in one direction and we can not use it in ac it is only for dc
    thanks
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Energy stored in dielectrics and gaps. I don't see it that way, but maybe you know something that I don't. Capacitors are used in AC applications all the time. Again you have theses quaint notions form somewhere, but that doesn't make them true.
     
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  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Well in a capacitor the dielectric is an insulator. The energy is stored in the electrostatic field between the plates which is also where the dielectric happens to reside.

    Your second question. Its the anode film that can't withstand reverse breakdown. The anode film is only applied to 1 plate. Non-polarized (or bipolar) capacitors do exist though..they are just expensive.
     
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  4. Papabravo

    Expert

    Feb 24, 2006
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    Air is a suitable dielectric. The presence or absence of a dielectric material changes the properties of the capacitor, but it is the field that stores the energy. Same deal for an inductor, air, iron, or ferrite core the energy is still in the field.
     
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  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    This only applies to one family of capacitors, Electroylitics.

    Aluminum Electrolytic are the little cans you see everywhere and are extremely common due to low price for high values of capacitance.

    Tantalum Electrolytics are solid/dry, they have a dipped look to them, and are physically smaller for the same value of capacitance, and a lot more expensive.

    The dielectric in both types is formed by an electrolyte on one side of the conductor, which makes the dielectric extremely thin, allowing more capacitor area in a given physical package. The electrolyte in Aluminum types is liquid, and a solid in Tantalum types.

    The downside of this method for creating very high values of capacitance is that the dielectric only "works" one way, and will allow current to pass in the reverse direction, causing heat/explosion from the electrolyte boiling (Aluminum) or burning (Tantalum aka "Exploding").

    Putting two capacitors in series, with the negative sides connected, creates a "non-polarized" capacitor, but with half the value of each individual cap due to two capacitors being in series. This is how non-polarized electrolytic capacitors are constructed internally, but are more expensive and only applicable in specific circuits, such as audio crossovers.
     
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  6. davebee

    Well-Known Member

    Oct 22, 2008
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    It takes energy to polarize the molecules in the dielectric of a capacitor when the charged capacitor sets up the electric field through the dielectric, so I guess you could say that the dielectric energy is stored by that polarization of the dielectric molecules.
     
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