1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Plasma ignition

  1. Jul 1, 2016 #1
    So I've been reading about how plasma cutters work, and the way it ignites intrigued me and got me thinking. My question is, how conductive would a stream of ionized air created by a high voltage spark be? If you passed a high current, low voltage through the stream, would it be able to travel along it? Is there an equation that can relate air temperature to resistance?
  2. jcsd
  3. Jul 2, 2016 #2

    Charles Link

    User Avatar
    Homework Helper
    Gold Member

    You can run relatively high currents at low voltages through ionized gases. This is what your neon lamps are and also fluorescent tubes. In the case of the fluorescent tube, you also have a fluorescent coating to convert the UV (much of the arc emissions are UV) that is emitted from the plasma arc to visible light. In order to get the arc started, it requires high voltages, but once the arc is started, you can get high currents (1 amp or more) at low voltages (typically 20 volts or less). The resistance drops significantly in a plasma as the current increases. In an arc lamp circuit, it often requires a ballast resistor to stabilize the current or the current can increase to very large amounts because the resistance drops as the current increases. Additional item is air in its neutral state has very high electrical resistivity but if it is highly ionized it actually becomes quite conductive.
    Last edited: Jul 2, 2016
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted