Why +ve terminal of electrolytic caps must be connected to +ve of battery?

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In summary, electrolytic capacitors must be connected to a higher DC potential in order to form the dielectric oxide layer, and should not be used where varying voltage comes across them. If you do not follow the polarity, the capacitor can become a conductor and explode.
  • #1
dexterdev
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Hi all,
I have a doubt regarding electrolytic capacitor. Why the electrolytic capacitor should be connected to higher DC potential in the circuit. What happens if the opposite happens? Also how electrolytic capacitors must be used where varying voltage comes across it?

-Devanand
 
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  • #2
There is a very thin insuating layer of Aluminium Oxide on one of the plates of the capacitor. This was formed by applying a voltage to the capacitor.

This layer is the dielectric of the capacitor, so it is very important.

So, it is important that you don't reverse the polarity as this can destroy this thin layer.

If you don't follow this polarity, the results get very messy.
I have never seen one of these explode, but I know they do because I have cleaned up the sticky mess that results. The capacitors vomit their entire contents as a steaming hot, foul smelling, sticky mess.

Just don't do it.

I have seen circuits where an electro is used for AC but I wouldn't do it. You can get non polarized capacitors and these should be used where high capacitance is needed.
 
  • #3
dexterdev said:
Hi all,
I have a doubt regarding electrolytic capacitor. Why the electrolytic capacitor should be connected to higher DC potential in the circuit. What happens if the opposite happens? Also how electrolytic capacitors must be used where varying voltage comes across it?
The oxide insulator is formed in the factory by electrolysis in the finished product, the oxygen reacts with the surface of the thin aluminium foil. If you reverse the working voltage, this oxide layer can be removed and the capacitor becomes a conductor.

For AC usage, two capacitors are joined back to back, so this means one oxide layer is always being enhanced by the polarity.

I've seen small electrolytics connected with reverse polarity disintegrate with a bang exactly like a fire cracker, throwing shredded material as from a firecracker everywhere, including in the student's hair.
 
  • #4
thankyou for replies.
 

1. Why is it important to connect the positive terminal of an electrolytic capacitor to the positive terminal of a battery?

The positive terminal of an electrolytic capacitor is marked with a "+" symbol, indicating that it is the side of the capacitor where electrons flow in during charging. Similarly, the positive terminal of a battery is also the side where electrons flow out. Connecting these two terminals ensures that the capacitor is properly charged and can function effectively.

2. Can I connect the positive terminal of an electrolytic capacitor to the negative terminal of a battery?

No, this is not recommended. Connecting the positive terminal of an electrolytic capacitor to the negative terminal of a battery can cause damage to both the capacitor and the battery. This is because the capacitor is designed to only allow electrons to flow in from one terminal, and connecting it to the wrong terminal can disrupt this flow and potentially cause a short circuit.

3. What happens if I reverse the polarity and connect the negative terminal of an electrolytic capacitor to the positive terminal of a battery?

If the polarity is reversed, the capacitor will not be able to charge properly. This can result in potential damage to the capacitor and may also cause the battery to overheat. It is important to always connect the positive terminal of an electrolytic capacitor to the positive terminal of a battery to ensure proper functioning.

4. Can I use an electrolytic capacitor with a DC power supply instead of a battery?

Yes, you can use an electrolytic capacitor with a DC power supply as long as the polarity is correct. However, it is important to make sure that the voltage of the DC power supply is within the rated voltage of the capacitor to avoid damaging it.

5. Is it safe to touch the positive terminal of an electrolytic capacitor connected to a battery?

No, it is not safe to touch the positive terminal of an electrolytic capacitor connected to a battery. The capacitor can hold a charge and can give you an electric shock if you touch it. It is important to handle capacitors with caution and to always discharge them before working with them.

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