novice: why do electrolytic capacitors...

Because they can only withstand the rated voltage the correct way around. They leak more with small voltages in the reverse direction as well.

Sorry, it can't be guaranteed that it won't work correctly.

Stupid metaphor of the day- consider a compressor storage tank- it can withstand internal pressure of 150psi but will crumple up on a vacuum (external pressure of 15psi).

Best regards, Spehro Pefhany

They make more noise one way than the other.

Why do electrolytic capacitors have to be connected the correct way around? Why does a circuit not work correctly if an electrolytic capacitor is reversed? Is it like a battery - only sinks rather than sources a charge?

Initially, current builds a very thin insulating layer on one electrode (just like anodisation of aluminium). Reversing the polarity reverses the process and so destroys the layer.

Search on "borax" and "rectifier" for the full story. You can think of an electrolytic capacitor as a really crappy diode that happens to have a lot of junction capacitance.

To answer this - I rather like the Japanese name for an electrolytic cap. They call it a 'chemicon' - i.e a chemical capacitor ( condensor ) .

It relies on electro-chemical processes to work correctly.

As such, it effectively has an anode and cathode. This is why it has to be used the right way round.

If you want more info - google is your friend !

Graham

I saw a guy test a power supply once, 20A at 50V unregulated, and the bloke building it had put all 4 filter capacitors in the wrong way round. Like a wedding!

Paul Burke

around? Why

reversed? Is

But probably a bit more messy... ;-) Btw. there's a "basic" group where all the "novice:" posings might be better off....

/Anders

Basically, yes. When reversed it acts as a very effictive current sink, but only for a fairly short time.

Why

Is

This is where you need to bring a supply up with a variac that has an AC current meter to monitor the current. The test procedures I wrote for linear power supplies with a bank of "Computer grade" capacitors explained the reason, and the danger of not doing it right.