capacitor that doesn't fully discharge - Page 1
Forum section: electronics / general

author: Raj
author_rank: Frequent Contributor
timestamp: September 11, 2019, 03:01:39 pm
content: I remember watching a video of some radio engineer, someone like Mr Carlson's lab.In it, the host charges capacitor,measures it shorts it, measures it, and even after shorting it, there is little voltage on the cap.it doesn't happen with other type of capacitor...he goes on to explain why one should avoid those in oscillators and all capacitance critical circuits.Maybe it was a fault of electrolytic capacitor but I wanna know what exact kind of capacitor was it. Bonus-link to the said video.

author: Raj
author_rank: Frequent Contributor
timestamp: September 11, 2019, 04:00:58 pm
content: excellent! thanks!

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 11, 2019, 04:08:17 pm
content: Yep.And also, will a capacitor ever *fully* discharge anyway...?

author: Benta
author_rank: Super Contributor
timestamp: September 11, 2019, 07:37:54 pm
content: Quote from: blueskull on September 11, 2019, 03:54:23 pmSpot on!Bob Pease (my sadly deceased electronics hero!) also called it "soakage":https://www.electronicdesign.com/analog/whats-all-soakage-stuff-anyhowEnjoy.

author: magic
author_rank: Super Contributor
timestamp: September 11, 2019, 09:55:39 pm
content: Quote from: SiliconWizard on September 11, 2019, 04:08:17 pmSend me one that doesn't, I will have a use for that.

author: John B
author_rank: Frequent Contributor
timestamp: September 11, 2019, 10:01:53 pm
content: Quote from: SiliconWizard on September 11, 2019, 04:08:17 pmCould be a good topic for one of those unrealistic theoretical thought experiment threads:"When an RC circuit is at the 10^287648563487th time constant, can the last electron ever leave the capacitor???"

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 11, 2019, 10:44:39 pm
content: Quote from: magic on September 11, 2019, 09:55:39 pmIn the sense the OP mentioned, obviously there are. That was his whole point. Of course that was teasing from my part. Apparently the smiley didn't help.And using that same context for any kind of cap, in any practical setting, you will have a pretty hard time getting one to exactly zero residual charge. It's all in the context.It's a pretty important and basic thing to know though. In many cases, it doesn't really matter, but in some specific use cases, it does (and can be pretty annoying to deal with, for instance for sample and hold circuits...)Obviously none of this, nor the OP's thread, means that there is unlimited free energy. Damn.

author: Red Squirrel
author_rank: Super Contributor
timestamp: September 12, 2019, 01:19:57 am
content: I just had a random idea.What happens if you hookup a batteriser to a capacitor? You basically get 800% more farads!

author: GlennSprigg
author_rank: Super Contributor
timestamp: September 18, 2019, 01:22:51 pm
content: Maybe just reverse the polarity for a micro second on the capacitor

author: Psi
author_rank: Super Contributor
timestamp: September 18, 2019, 02:43:12 pm
content: It can be quite dangerous for really huge high voltage capacitors. It's why they're always stored in a shorted state.A 0.1% self recharge on a 1000V capacitor the size of a refrigerator is still a significant amount of energy at 1000V.You really don't want to touch that.