# 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
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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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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.