Simple question about capacitor

Thread Starter

Bamerni

Joined Jun 26, 2016
53
Hello everyone

I just have a simple question but I don't know it's answer

what is the effect of capacitor polarity in electronic circuit, because as I know capacitor is a passive element like resistors and inductors, so you the put the polarity of the capacitor in circuit diagrams.

thanks in advance
 

AlbertHall

Joined Jun 4, 2014
11,524
Electrolytic capacitors have a defined polarity. If they are reversed they will be damaged/destroyed. They use a layer of oxide on one electrode as the insulator and the correct polarity maintains the oxide layer. When reversed the oxide layer is removed and the capacitor begins to pass current which it should not do.

Capacitors other than electrolytics use such as paper, plastic film, ceramic as insulators and with these polarity doesn't matter.
 

Thread Starter

Bamerni

Joined Jun 26, 2016
53
Electrolytic capacitors have a defined polarity. If they are reversed they will be damaged/destroyed. They use a layer of oxide on one electrode as the insulator and the correct polarity maintains the oxide layer. When reversed the oxide layer is removed and the capacitor begins to pass current which it should not do.

Capacitors other than electrolytics use such as paper, plastic film, ceramic as insulators and with these polarity doesn't matter.
Thank you for your reply, that is mean I can change the Electrolytic capacitors with other type of capacitor without effecting the circuit function
 

Thread Starter

Bamerni

Joined Jun 26, 2016
53
Electrolytic capacitors have a defined polarity. If they are reversed they will be damaged/destroyed. They use a layer of oxide on one electrode as the insulator and the correct polarity maintains the oxide layer. When reversed the oxide layer is removed and the capacitor begins to pass current which it should not do.

Capacitors other than electrolytics use such as paper, plastic film, ceramic as insulators and with these polarity doesn't matter.

Ok, why some times changing the polarity of Electrolytic capacitors in a circuit didn't effect its function, is that depend on the circuit or capacitor
 

AlbertHall

Joined Jun 4, 2014
11,524
Thank you for your reply, that is mean I can change the Electrolytic capacitors with other type of capacitor without effecting the circuit function
I can't think of a circuit which works with an electrolytic that wouldn't work just as well with a non-polar capacitor of the same value.
 

AlbertHall

Joined Jun 4, 2014
11,524
Ok, why some times changing the polarity of Electrolytic capacitors in a circuit didn't effect its function, is that depend on the circuit or capacitor
If the reverse voltage is well below the voltage rating of the capacitor then it will work for a while but it will eventually fail.
 

WBahn

Joined Mar 31, 2012
26,398
Ok, why some times changing the polarity of Electrolytic capacitors in a circuit didn't effect its function, is that depend on the circuit or capacitor
Because you got lucky. If the reverse voltage isn't too much, then some capacitor types can handle it, at least for a while. Other types, particularly tantalums, tend to fail catastrophically by either bursting into flame or exploding.
 

wayneh

Joined Sep 9, 2010
17,153
Thank you for your reply, that is mean I can change the Electrolytic capacitors with other type of capacitor without effecting the circuit function
No one would use polarized electrolytic capacitors if they didn't offer the advantage that @MaxHeadRoom just gave in #7 – high capacitance per unit of size and cost. If you need, say 47µF of capacitance for your circuit, it would be expensive and impractical to use other types unless absolutely required.

No one would use electrolytics otherwise because they have a shorter life, require care to avoid reverse polarity, are electrically leaky (they self-discharge) and are slow and not as effective at high frequency. But they win on size and cost.
 
An electrolytic works up to about 1.5 volts in reverse, after that it goes short circuit.
Some people use two electrolytic's back to back to make them bi-polar.
 

ScottWang

Joined Aug 23, 2012
7,070
thank for your reply, what do you mean by back to back?
It means that they connected like as (-)--||--(+)-----(+)--||--(-) or (+)--||--(-)-----(-)--||--(+), if the original is a Polarized Electrolytic Capacitors and then it will become a Non-Polarized Electrolytic Capacitor, but the values of capacitance is only 1/2 of the original values.
 
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