Connected the capacitor to a DC power supply

AI Thread Summary
Connecting a capacitor to a DC power supply with reversed leads can cause it to pop, even if the voltage is within its rated limits. This occurs because electrolytic capacitors rely on a thin oxide film that can break down when polarity is reversed, leading to large currents and overheating. In contrast, when connected to an AC power supply, the alternating current allows the capacitor to charge and discharge without sustaining damage, as the voltage polarity changes continuously. The discussion highlights the importance of understanding capacitor types and their behavior under different power supply conditions. Proper handling of capacitors, especially electrolytic ones, is crucial to avoid dangerous failures.
unseensoul
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A few days ago, I was in the lab doing some experiments with capacitors and something weird happened...

I connected the capacitor to a DC power supply and after a few seconds the capacitor has popped. The voltage applied to it was within its working voltage, so that was not the cause. My lecturer then told me that I connected the leads to the capacitor the other way round and he was right. Then I asked him the following question in which he was unable to answer it...

If I have a DC power supply and connect the leads to the capacitor in the wrong way, it will pop! This means that the current is only allowed to flow in one direction... So why don't they pop with an AC power supply?
 
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What make you think they don't?
 
Probably, they do, but that's not my question...
 
unseensoul said:
So why don't they pop with an AC power supply?

unseensoul said:
Probably, they do, but that's not my question...

Only question I see. Your proceeding statement is correct.
Perhaps you can clarify what your question is then.

Edit: Ok, Not thinking. Charge can move into and out of the cap as long as the voltage polarity remains the same.
So your proceeding statement is not quite correct.
 
Last edited:
I would assume that the capacitor to which you refer is an electrolytic...

Aluminium Electrolytic capacitors rely on the thickness of a film of oxide formed on the plates inside the capacitor.

Unless the electrolytic is a reversible type, the thickness of the oxide films on the positive & negative films is different.

Therefore, when the capacitor is reversed, the thinner film breaks down, large currents flow & the electrolyte heats up.

Then the can pops.

This is dangerous... the bigger the capacitor, the more dangerous it is...
 

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