Experimenting with Capacitor Discharge Arcs: What's Going On?

Click For Summary

Discussion Overview

The discussion revolves around the phenomenon of capacitor discharge arcs, specifically the experience of a participant who observed their capacitor terminals becoming stuck together after discharging. The conversation explores the implications of this behavior, safety considerations, and personal anecdotes related to capacitor use and experiments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes their experience with capacitor discharge arcs and the unexpected sticking of terminals after discharging a 340μF capacitor at 9V.
  • Another participant suggests that the sticking is due to arc welding of the wire ends.
  • A later reply humorously acknowledges the suggestion and mentions potential savings in lead and electricity.
  • Concerns are raised about scaling up the experiment, highlighting that large currents can occur and pose risks, including the potential for capacitor explosions.
  • One participant shares a personal anecdote about a dangerous experience with a high-capacitance capacitor and the importance of ensuring capacitors are properly discharged before handling.
  • Another participant notes that their smaller capacitors typically only pop and are harmless unless mishandled, sharing a childhood experience with a transformer that resulted in a dangerous situation.

Areas of Agreement / Disagreement

Participants express varying levels of concern regarding safety and the behavior of capacitors during discharge. While some agree on the risks associated with high currents, there is no consensus on the specific mechanisms behind the sticking terminals or the best practices for handling capacitors.

Contextual Notes

Participants reference personal experiences and safety considerations without providing detailed technical explanations or mathematical analysis of the phenomena discussed.

Who May Find This Useful

Individuals interested in experimental electronics, capacitor behavior, safety in electrical experiments, and personal anecdotes related to electrical engineering may find this discussion relevant.

PhysicoRaj
Gold Member
Messages
538
Reaction score
49
Hi there..
I was experimenting with capacitor discharge arcs. I charged a 340μF cap to 9v and shorted the terminals of the cap. Zap! Sparks!.. Then the terminals got stuck to each other as if they had been glued together! It took me 3-4 seconds pulling at them to separate them. It happens every time I do it and with all other caps. Can anyone tell me what's happening here?
 
Last edited:
Physics news on Phys.org
you are arc welding the ends of the wires together

Dave
 
  • Like
Likes   Reactions: 1 person
Why.. yes.. Thanks a lot Dave, I'm going to save 500 g of lead and 2.25 kWh of electricity every year now onwards. :cool: :biggrin:
 
Be careful if you decide to scale up the experiment. The current is only limited by the resistance of the wire and any resistance in the capacitor. Very large currents are possible with the right capacitors and they have the potential to explode (although connecting them with reverse polarity is a better bet if you actually want them to explode).
 
CWatters said:
Be careful if you decide to scale up the experiment.

Very true. I remember once working on a mains-powered amplifier where the smoothing caps were something like 40,000 uF at 50V.

Before attacking it with a soldering iron, I decided to check the caps were properly discharged by shorting the terminals with a screwdriver.

There was a loud bang, and the screwdriver was a few millimeters shorter, and bladeless.
 
I've only caps of a few hundred microfarads, a combination would fetch around a max of 5 mF. I have worked with these and they only pop, and harmless unless you hold your face right into them. The worst experience I had was when I was a small boy, I tried making a step up transformer by connecting a 240v-6v step down transformer in the reverse way! I plugged the 6v secondary ends to the 240v mains and waited for the 9600v arc at the primary. But before I could even wait the fireworks had been unleashed... Even today I triple check everything when i hear 'transformer'
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
5
Views
3K
  • · Replies 14 ·
Replies
14
Views
6K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 6 ·
Replies
6
Views
6K
  • · Replies 15 ·
Replies
15
Views
5K
  • · Replies 32 ·
2
Replies
32
Views
9K