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Light bulb in a microvawe oven

  1. Nov 26, 2015 #1
    I'm sorry to reopen the debate on what happens when I put a light bulb in a microvawe oven, but the question is driving me crazy.
    I'm debating with other students about "why I light bulb lights up when I put it in a microwave oven ?".
    I read the old thread posted in 2003 https://www.physicsforums.com/threads/light-bulb-in-a-microwave.6438 [Broken] - I found a lot of nice conclusions about, but some of them are in contradiction.
    Duncan states that "The incandescent bulb is likely to be lit due to current in the filament set up by the microwaves directly. Microwaves waves applied to metals will in general create electric currents".
    But chroot objects by stating that "Microwaves applied to metals do not create currents. Furthermore, your assertion that the arcing due to foil is caused by such currents is also wrong" (and I agree with him).
    Can anyone put the "end" word to this question by explaining why the light bulb lights up ?
    Many thanks in advice.
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Nov 26, 2015 #2


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    Why should an EM wave not cause currents to flow in a conductor? It works for lower radio frequencies. A typical lamp filament and supporting wires is pretty much the same size as the wavelength of around 12cm and it can be near resonance, which can cause the induced currents to be high. Once the (very thin) filament gets hot, the gas around it can also get excited and become ionised due to the high temperature and EM fields. Then the whole bulb can be filled with attractive looking wavy arcs. You have several hundred Watts of microwave power available and the filament may only be designed to handle, say 60W so it will glow at a much higher temperature than it would normally do.
  4. Nov 26, 2015 #3


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    which is completely incorrect

    If that were the case, then we couldn't/wouldn't have microwave radio transmitters/receivers for communications
    Your satellite TV ( if you have it) comes to you via a microwave transmitter on the satellite. That microwave radio signal generates/induces currents
    in the antenna that is part of the dish antenna at your/your neighbour's home

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