Does plasma maintain a charge when current flows through it?

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Discussion Overview

The discussion revolves around the behavior of plasma in relation to electric current and its potential to maintain a charge. Participants explore the implications of plasma's conductivity and its interaction with magnetic fields, as well as the feasibility of using plasma in capacitor designs.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether plasma becomes positively or negatively charged when current flows through it and whether it could be used in capacitor construction.
  • Another participant suggests that plasma can have a tiny net charge, but typically these charges are negligible and questions the relevance of capacitance in such a scenario.
  • A different viewpoint emphasizes that plasma is always affected by magnetism and is generally highly conductive, noting that charge in plasma tends to neutralize due to ion rearrangement, although a positive charge can exist near plasma-wall boundaries due to the formation of a Langmuir sheath.
  • This participant also points out that while capacitors are generally thought not to carry DC current, plasma can sustain a DC current due to its conductivity.

Areas of Agreement / Disagreement

Participants express differing views on the nature of charge in plasma and its implications for capacitor design. There is no consensus on whether plasma can effectively maintain a charge or be used in capacitors.

Contextual Notes

Participants note that the behavior of plasma regarding charge and current flow may depend on specific conditions, such as the presence of boundaries and the nature of the current.

TheEllimist
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I've been looking through the internet and so fair I haven't found anything too clear on this. Some articles have said that plasma can be affected by magnetism and can be conductive, but my question is, will it become positively/negatively charged while current is flowing through it, and if it does would it be possible to make a capacitor with one or more plates being made of/holding plasma?
 
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It can have a tiny net charge both with and without current flow, but typically those are negligible.
TheEllimist said:
and if it does would it be possible to make a capacitor with one or more plates being made of/holding plasma?
Not with any relevant capacitance.
 
Thanks.
 
"can be" suggests that it is only sometimes true. Plasma is always affected by magnetism and is generally very highly conductive. It's hard to have much charge in most plasmas because the ions will rearrange and neutralize the charge, but you do generally have an excess of positive charge near a plasma-wall boundary due to formation of a Langmuir sheath. Normally, we think of a capacitor as something that won't carry DC current, but a plasma is very conductive and will easily sustain a DC current.
 

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