We just had an OSHA trainer tell our group that a capacitor can be recharged by, I paraphrase, "ambient static electricity," thereby creating a potential hazard. Is this a documented phenomenon?
If undocumented, does it seem physically possible?
I googled it briefly and nothing popped out immediately. What did he really mean?
Possibly related: Charge capacitor with static electricity -- Haven't had time to review this yet
It would really depend on what the source impedance of the electric field is, if it's air which has resistance of well over 10^9Ω in most cases, then it probably would not be a high enough impedance to charge the capacitor as the leakage of most capacitors is most likely in the uA to nA range and (lower than 10^9 ohms).
In addition, just having a capacitor 'sit there' with both terminals exposed to air probably wouldn't have much of an effect on the voltage of the terminals as they would be exposed to the same field and same\simmilar potentials. One would need a setup where one of the terminals could 'collect' current from the air and the other be grounded (or at least a much lower potential than the terminal connected to air)
I would think that the resistance in the capacitor would bleed off any small currents from most ambient static electric fields. If you had a much stronger source, like a van de graff generator, and placed it close to the cap you could probably charge it and create a 'semi' hazardous voltage on the capacitor (but it probably wouldn't be any different than touching the van de graff generator)
It is a concern that capacitors can develop a dangerous charge and be discharged when handled (many devices are designed to 'bleed of' charge in less than 30 seconds of operation so they are safe to open/repair).
E fields can charge tiny capacitance with a leakage path, so de-ionizer's and/or setting RH to 50% are employed to make the environment more EOS safe.
If anyone has put Xmas tinsel near a TV tube, just turned off will see the tinsel capacitance rise in charge level with the angle of the tinsel.
Ben Franklin tried to use lightning power to store charge with a kite. It didn't work, and he was lucky it didn't ;)
But yes it can but depends on how low leakage it is , or the quality factor of the plastic as the dissipation time can be pretty quick. It takes triboelectric action to create a charge imbalance and and a bipolar de-ionizer or high humidity > =50% to neutralize or balance the charge.
As I recall TEK Diff Probes with 1pF and FET's rated for 25V would blow from EOS just moving the wand and looking sideways. (I'm just kidding. The tech who repaired it so often, said she was tired of fixing it so often ;) Although when I implemented a EOS protection plan plant-wide in the early '80's, a charge meter recorded 200V on my finger just from raising one foot off a nylon carpet after grounding myself. Q=CV so a change in body capacitance to carpet C , Q/C=V
