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

  • Thread starter Thread starter dexterdev
  • Start date Start date
  • Tags Tags
    Battery
Click For Summary

Discussion Overview

The discussion revolves around the proper connection of electrolytic capacitors in circuits, specifically addressing the necessity of connecting the positive terminal of the capacitor to the higher DC potential of a battery. Participants explore the consequences of reversing this connection and the implications for varying voltage applications.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants explain that the insulating layer of Aluminium Oxide on one plate of the capacitor is crucial and formed by applying a voltage, making correct polarity essential.
  • Others note that reversing the polarity can destroy the oxide layer, potentially leading to catastrophic failure of the capacitor, including messy and hazardous outcomes.
  • A participant mentions that for AC applications, two electrolytic capacitors can be used back to back to maintain the oxide layer's integrity.
  • Concerns are raised about the dangers of using electrolytic capacitors with reverse polarity, including explosive failures and the scattering of debris.

Areas of Agreement / Disagreement

Participants generally agree on the importance of maintaining correct polarity for electrolytic capacitors and the potential dangers of reversing it. However, there are varying opinions on the use of electrolytic capacitors in AC applications and the specifics of failure modes.

Contextual Notes

The discussion includes assumptions about the behavior of the oxide layer under different conditions and does not resolve the nuances of using electrolytic capacitors in varying voltage scenarios.

Who May Find This Useful

This discussion may be useful for electronics enthusiasts, students learning about capacitors, and individuals working with circuits involving electrolytic capacitors.

dexterdev
Messages
194
Reaction score
1
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
 
Engineering news on Phys.org
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.
 
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.
 
thankyou for replies.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 17 ·
Replies
17
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 12 ·
Replies
12
Views
1K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 15 ·
Replies
15
Views
5K
  • · Replies 19 ·
Replies
19
Views
6K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 3 ·
Replies
3
Views
4K