3 ms·

The fun is that capacitors work even when power is off, so if they had several caps together and one was the wrong way round or the power supply was off but not

by zaarn 7y ago

The fun is that capacitors work even when power is off, so if they had several caps together and one was the wrong way round or the power supply was off but not disconnected OR the capacitor was already charged beyond a point of no return, it'll blow. While they look fairly harmless, one should also never forget that capacitors are the most dangerous part of any electric circuit; they don't become safe if power is off and they have no limit to their current other than "what the wire can do", which is usually northwards of "the wire evaporates". I've experienced various caps burn their legs and solderpoints in less than a millisecond without warning once a short was realized. And on top of that, the huge currents running through wires not intended for that will usually cause quite a bit of inductive backlash in nearby components.

jacquesm 7y ago
I've worked with capacitors that were designed to dump their charge in a few us. You really do not want to mess with that stuff without proper precautions, nothing scares me more than a couple of hundred volts power source with an Ri too low to measure. You need to forcibly restrain your cabling or it will jump all over the place during a discharge.
mikevp 7y ago
Heh... Recalling a demonstration by an EE prof way back when. He had the bank of capacitors charging up on his desk, and was writing on the blackboard the equations of how much energy was stored. Hand raised in the back of the room. "Uh, Dr. Miagawa, I think you slipped a decimal point there." Prof looks over his work again, says "Oh, dear" unplugs the charger and backs away. He tapes two meter sticks together with a screwdriver on the end to discharge his little electrobomb. WHAMO, screwdriver vaporizes. I'm pretty much convinced this was not a mistake, it was a "Be really CAREFUL with this stuff!" object lesson.
velosol 7y ago
And of course you can harness this all to shrink coins [1]. [1]: https://www.youtube.com/watch?v=tCh8UoLY-ow https://www.youtube.com/watch?v=tCh8UoLY-ow

by zaarn 7y ago

jacquesm 7y ago

I've worked with capacitors that were designed to dump their charge in a few us. You really do not want to mess with that stuff without proper precautions, nothing scares me more than a couple of hundred volts power source with an Ri too low to measure. You need to forcibly restrain your cabling or it will jump all over the place during a discharge.

mikevp 7y ago

Heh... Recalling a demonstration by an EE prof way back when. He had the bank of capacitors charging up on his desk, and was writing on the blackboard the equations of how much energy was stored. Hand raised in the back of the room. "Uh, Dr. Miagawa, I think you slipped a decimal point there." Prof looks over his work again, says "Oh, dear" unplugs the charger and backs away. He tapes two meter sticks together with a screwdriver on the end to discharge his little electrobomb. WHAMO, screwdriver vaporizes. I'm pretty much convinced this was not a mistake, it was a "Be really CAREFUL with this stuff!" object lesson.

velosol 7y ago

And of course you can harness this all to shrink coins [1]. [1]: https://www.youtube.com/watch?v=tCh8UoLY-ow https://www.youtube.com/watch?v=tCh8UoLY-ow