I am wondering what makes a polarized capacitor physically different than a non-polarized capacitor. I am aware they are functionally different.

I understand the physics of a non-polarized capacitor, but what materials or configuration makes a polarized capacitor operate differently in different orientations?? I am also aware it is different in AC and DC circuits?


The electrolytic capacitor is the usual example of a polarized capacitor. It’s made with plates of two dissimilar metals and an electrolyte between.

If voltage is applied one way, electrochemistry causes a very thin nonconducting oxide to form on one plate. That oxide acts as a very thin dielectric, so you get a high capacitance value.

If applied the other way, the oxide lifts off and is destroyed: no insulator, no capacitance and soon no capacitor.

You have to use these with a DC bias larger than the signal, so that as the DC+signal total voltage varies it never changes sign.

  • $\begingroup$ Thanks! So does the oxide act as the dielectric? $\endgroup$ – Dustin K Jun 15 at 6:42
  • $\begingroup$ Right! I edited the answer to make that clearer. $\endgroup$ – Bob Jacobsen Jun 15 at 7:10

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