Why do some capacitors have polarity?

AI Thread Summary
Capacitors like electrolytic and tantalum types have polarity due to their construction and the chemical processes involved in storing charge. When reverse-bias voltage exceeds 1 to 1.5 V, it can damage the dielectric layer, leading to short circuits and potential explosions. The charge storage mechanism in polarized capacitors relies on electrolytic chemistry, necessitating a specific positive and negative terminal. Improper connections can result in catastrophic failures, as evidenced by personal experiences of explosions when connected incorrectly. Understanding these characteristics is crucial for safe and effective use of polarized capacitors.
sinanissa
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Really, after I became an electrical (control) engineer, until now i do not know why capacitors like Electrolytic and Tantalum Ones, have polarity. can anybody answer me please?
 
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From http://en.wikipedia.org/wiki/Electrolytic_capacitor"

"This is necessary because a reverse-bias voltage above 1 to 1.5 V[1][2][3] will destroy the center layer of dielectric material via electrochemical reduction (see redox reactions). Without the dielectric material the capacitor will short circuit, and if the short circuit current is excessive, then the electrolyte will heat up and either leak or cause the capacitor to explode."

And this explosion really happened with me once I connected a 1000 F capacitor to a car battery in reverse, it exploded, like a fire cracker!
 
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The characteristics has something to do with the chemistry of holding up the charges.
In Polarised caps , the charge principle is based on electrolytics. Hence one end has to be positive and the other negative.
 

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