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Electric discharge - Sound?

  1. Nov 26, 2005 #1
    Hi all,

    everyone has experienced electric shocks when discharging oneself, for example when you have clothes made of wool and take them off, or if you touch a metal object after walking across a carpet.

    My question: Why do you hear the discharge? I've noticed when getting the laundry out of the dryer, you hear the "sparks".
  2. jcsd
  3. Nov 29, 2005 #2
    Electrons moving through the air strike the molecules in the air, heating them up. In the case of a spark there are a lot of electrons causing a lot of heating. The air expands rapidly and then once the electrons stop heating the air cools rapidly and "snaps" back together. The sound you hear is just air hitting air, the exact same thing as thunder but on a much smaller scale.
  4. Nov 29, 2005 #3
    The basic idea behind the concept is correct but 'm afraid not everything what you said. It is not because of an air molecule hitting another air molecule.Sudden change in temprature cause expansion in the air which in turn leads to a sound wave or the crackling noise you hear.
  5. Nov 29, 2005 #4
    Thanks for your replies Geoff St. Germaine and .:JimmY:..
    It's somehow funny that you can hear those mini-lightnings.
  6. Nov 29, 2005 #5
    A sound wave is molecules of air pushing and pulling other molecules of air. That's how sound moves through any medium.
  7. Nov 29, 2005 #6
    How do you think that the temperature change causes the expansion?
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