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I have two 100uF electrolytic capacitors. Same voltage rating and same temperature rating, yet one is 8 times larger than the other one, being 2x longer and having 2x the diameter.

If I want to use one of them as a filter capacitor, will the physical size affect how good a job it does getting rid of high frequency noise?

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  • \$\begingroup\$ Are they both polarized caps? \$\endgroup\$ – Spehro Pefhany Apr 17 '16 at 0:31
  • \$\begingroup\$ @SpehroPefhany I doubt a non polarized 100uF exists at all. \$\endgroup\$ – Bregalad Mar 3 '17 at 8:35
  • \$\begingroup\$ @Bregalad They certainly exist, but they tend to be relatively large for the voltage rating. \$\endgroup\$ – Spehro Pefhany Mar 3 '17 at 13:14
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If they are of the same age and technology the larger one will have lower ESR so there will be significantly less heating due to ripple current so it will at normal temperatures last longer. The life of an electrolytic capacitor is quite reasonable at normal temperatures but ripple current causes self-heating that reduces life dramatically. On the old 50/60 Hz stuff, the caps had to be so huge that the extra temperature rise due to ripple could be neglected. When restoring old gear it's surprising to see how long those large electrolytics lasted.

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You will probably find that the larger one has a higher ripple current rating and a lower equivalent series resistance.

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New and old caps (over a span of decades, say) with otherwise similar ratings may be of wildly different sizes due to improvements in manufacturing. The newer one will also be less likely to be dried out.

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  • 2
    \$\begingroup\$ You didn’t answer the question. \$\endgroup\$ – Incnis Mrsi Aug 24 '16 at 15:41

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