So, my circuits professor described electrolytic capacitors today, and said that reverse-biasing them could cause a catastrophic, eye-popping explosion. All that in a little metal can? I had to try it! Here's what it takes:

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Patrik8 years ago
Huh - I was just wondering the other day why there was an X scratched in the top of those electrolytic caps - I guess you just found out why: it's an intentional weak point to keep them from exploding! I don't remember seeing this on older caps, so you may be able to scrounge up an old one that is more explosion-prone...
Goodhart Patrik8 years ago
Oh yes, in the day of the cardboard and wax caps, they had this habit of either leaking or blowing their guts all over the inside of radios that did not have well regulated power supplies. I still have a few of those beasts at home; and a few "full metal jacket" 'can' capacitors that have no "weak spots" on them (some the size of a quart can of motor oil) and one "oil filled cap" that is nearly the size of a canteen. Heavy metal outsides to these guys, overloading them turn them into lethal grenades. Nothing to mess with for sure.
shouldn't a wax cap make a wax bomb? Contents heat up, under pressure, steaming wax is leaked. Capacitor shorts out, creating a spark\ kaboooom
Yes, and hot semi-solid wax all over the insides yuck
like lava lamps. another interesting question: what about oil filled caps?
I never drove them "over the top" as they were very high voltage / high powered caps. Overdriving such could create a "grenade" situation I am afraid.
Patrik Goodhart8 years ago

You seem to have missed the point of this thread! :-D
Goodhart Patrik8 years ago
If I set off something inside the Apt. that could put a hole in the old plaster walls and keep going into the neighbor's house, I am afraid you would not hear from me for awhile :-) Maybe once I get out into the country again, where I grew up......hmm, nah, I still won't do it LOL
plus the fire hazard......... your friends house is a much better place.
I have heard milder things explode. I really don't feel the need to take out a 2 inch thick plaster wall LOL What would I put between it and me ? Plexiglas ? No thanks. :-)
greek fire bombs come to mind here
stasterisk (author)  Goodhart8 years ago
heavy, metal outsides? or heavy metal outsides?
heavy, metal outsides?
or heavy metal outsides?

there is also :
- Heavy metal oxides.
- Hey we met all outsides.
- Ivy meat hall looks sides. (this one particularly makes no sense to me)
And if you are old enough to remember: that was "Reeeeal heavy man" LOL and I made an even further PUN on the artillery round designation of Full Metal Jacket.
Oh, the outside can was made of a heavy gauge metal, not of U238 or anything ;-)

Not like this: Complete AC Gilbert Atomic Energy Lab
Also, some bad-quality and cheap electrolytic capacitors tend to naturally inflate (and leak) with time. The 'X' avoids dangerous explosions, and let escape gases and liquids.

Capacitor plague
westfw8 years ago
I have a fond but faint memory of an EE lab in college. Someone had connected an electrolytic backward. "BAM!" I heard. There was confetti, I think. And someone saying "I don't want to be an engineer any more!"
Goodhart westfw8 years ago
:-) When I was younger, I hooked up a line that I "thought" would charge my homemade battery with a resistor in-line, and when I plugged it in, the resistor exploded like one of those small firecrackers one gets in some parts of the country. I learned not to do things before I knew what I was doing LOL
Patrik Goodhart8 years ago
I suspect the number of electrical engineers who haven't accidentally (*) blown up something in their career is vanishingly small. ;-)

(*) Given an appropriate definition of "accidentally", which includes "stupidly", "arrogantly", and occasionally - "intentionally"...
i blew up a psu in an unrivaled fit of stupidity. for a week after that, i didnt go near electronics.
Goodhart Patrik8 years ago
I have a few of these at home, it they would be hard to overdrive with my equipment :-)

Some HV Oil filled Caps.
Part number/ nominal voltage
SCR563 1 3,000
SCR564 2 3,000
SCR565 5 3,000
zachninme8 years ago
On the other hand, I now feel slightly safer knowing that they won't explode under low-volatages & low amps :P
stasterisk (author)  zachninme8 years ago
well, play around. It was a 4.7 mF cap (4700 uF)
Brennn108 years ago
Oh no, you busted a cap!
Kiteman8 years ago
Hey, it's The Little Capacitor That Could!
Hmmm I have an amusing plan to implement now...
LinuxH4x0r8 years ago
I used to do this all the time with a drill battery. -Then I found a can of gas!