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Neon and polarity measurement

  1. Nov 19, 2013 #1
    Hi All,

    I would like to know why the neon lamp is used to measure electrical polarity. What is the working mechanism involved.

    Best wishes,

  2. jcsd
  3. Nov 28, 2013 #2
    Could it be a question more appropriatedly posted in the quantum mechanics section?
  4. Nov 28, 2013 #3


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    Gold Member

    Neon lamps create light by glow discharge, and when DC current passes through, only the negatively charged electrode of a test lamp glows.

    If your question is more what makes it glow, this is due to the ionization of the atoms, producing free electrons and creating a plasma state.

    More from Wiki's:

    Is this what you were aiming for?
  5. Dec 7, 2013 #4
    Thank you TumblingDice, for your response.

    My problem with your answer is that I have the ideia that, in simple electric circuits, when the current starts, I used to think that the current will be established in all positions basically at the same time, and not only near the negative pole of the battery. Thus, it seems reasonable to me that, in a discharge lamp, when the negatively charged electrode starts sending its electrons, the glow would appear also in all positions of the electron's path to the positively charged electrode.

    Best Regards,

  6. Dec 7, 2013 #5


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    Neon lamps glow at the negatively charged electrode. They do not glow along a "path" like neon signs. From the first wiki link:
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