Capacitor Size

Discussion in 'General Electronics Chat' started by Prabu1004, Apr 17, 2013.

  1. Prabu1004

    Thread Starter New Member

    Apr 17, 2013
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    One doubt on the Capacitor Size.
    By theory, larger the value of capacitor can be obtained if the distance of separation between the two plates are smaller. C = εA/d
    But in general, larger value capacitors are bigger and larger in size. Why ?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Because to get more capacitance requires more plate area (A), given that the distance between plates (d) is reduced as much as practical for a given dielectric. Since electrolytics use a very thin chemical dielectric to give the minimum practical distance between plates, they have the largest capacitance of any capacitor type for a given physical size.
     
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  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,392
    1,606
    One interesting rule of thumb that follows for this is the size of a cap can be estimated from one cap of that series. As crutschow correctly states the plate size for a given capacitance follows from the dielectric, since a minimum spacing must be maintained for a given voltage.

    The rule of thumb is for a given series voltage x capacitance is proportional to the physical size.

    So say you have a 10 uF 10V cap, but need a larger voltage. A 10 uF 20V cap would be larger, but if you could get something close to a 5uF 20V cap it should come in the same case size.
     
  4. #12

    Expert

    Nov 30, 2010
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    6,817
    Saying the same thing in a different way, the manufacturers always use the closest spacing they can for a given voltage rating, then add more area to get larger amounts of capacitance.

    Great advancements have been made in thin film (insulator) technology in the last 20 years. Capacitors are a LOT smaller than they were 20 or 40 years ago, but 100 uf still requires 10 times as much total area as a 10 uf capacitor.
     
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