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I couldn't find a duplicate-like of this question. I'm also not sure whether this is an electrical engineering question or a physics question.

As most of you noticed when one needs to use larger capacitor values the type of capacitors available to use are polarized capacitors such as tantalum or electrolytic capacitors.

What is the relation between large capacitance and being manufactured polarized? is that the same reason: if we ask why are capacitors with small values are manufactured non-polarized?

user16307
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  • None, its different technologies and just the limitations of it – PlasmaHH Jun 17 '16 at 14:15
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    Because some technologies simply can't be manufactured in large capacitances without being physically **huge** or simply infeasible to manufacture. The technologies with the highest volume-to-capacitance ratios are typically the polarised ones. – Tom Carpenter Jun 17 '16 at 14:17
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    Capacitor polarization is never an advantage. You don't manufacture them because you *want* to, you manufacture them because you *have* to. – Ignacio Vazquez-Abrams Jun 17 '16 at 14:22
  • @PeterJ Do you "really" think these questions are duplicate? They ask the same thing? – user16307 Jun 17 '16 at 14:29
  • @user16307 the question isn't the same but the answer covers it - "The only reason people use polarized caps is because they often cost much less than non-polarized caps of the same capacitance and voltage rating" – PeterJ Jun 17 '16 at 14:32
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    well, inversely, as non-polarized caps tend to get cheaper to make(namely MLCCs), I see less and less usage of <10uF eletroytic caps (except in ultra cheap stuff) – Wesley Lee Jun 17 '16 at 14:34
  • @PeterJ I'm not asking why people use polarized caps. I'm asking why they(large value ones) can only be manufactured as polarized. Do you still insist it is duplicate? – user16307 Jun 17 '16 at 14:38
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    @user16307, what makes you think they can't be manufactured? I'd imagine a MLCC could be made in just about any value but do you think they'd be a market for say a 470uF $500 device? – PeterJ Jun 17 '16 at 14:46
  • @PeterJ Im asking a question – user16307 Jun 17 '16 at 14:47

1 Answers1

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Capacitance is dependant upon;

(1) the area of the plates,

(2) the inverse thickness of the di-electric or insulator between the plates

(3) the permittivity of the di-electric or insulating layer.

To make large value capacitors which don't require enormous plate size you need to have a very thin insulating layer with high permittivity.

Electrolytic construction requires the capacitor to be polarised to maintain the insulating oxide layer created by action of the electrolyte on the metal.

Reversing the polarisation will destroy the insulation and create a short circuit.

enter image description here

N.B. Unpolarised capacitors can be made with high values but will be be physically larger than their electrolytic companions value for value.

JIm Dearden
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