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I bought Dominos Choco Lava Cake and I had to warm it in my microwave oven. I could see that the cake was wrapped in aluminium foil, I put it in inside the oven and when I switched it on electricity was created inside the oven. It was like electricity was flowing through some high voltage wire. I could even see those violet (or purple) colour sparks.

Microwave oven sends out the electromagnetic waves and this waves can socialite the charged particles (that’s the way it warms food, it oscillates the polar water molecules). As aluminium is a metal and from books I have studied that metals have free electrons and hence conduct electricity. So, is it right to infer that aluminium has free electrons from what I observed?

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    $\begingroup$ putting metal inside a microwave oven and turning it on is dangerous, can cause fire, and I would strongly discourage you from doing this $\endgroup$
    – user245141
    Commented Feb 18, 2020 at 16:01
  • $\begingroup$ @yu-v Yeah I switched it off right at the moment. $\endgroup$
    – user240696
    Commented Feb 18, 2020 at 16:10

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No piece of matter that is neutral has free electrons. Conductors, and aluminum is a conductor, have some electrons that are bound to the total lattice, and are free to move within the lattice, and as part of a circuit . A microwave oven food plate does not close a circuit.

When irregular concentrations of metal are hit by the microwaves, the electrons in the Fermi level move so that high electric fields can produced,which ionize the air and create sparks. The electrons come from the air.The heat can also set fire. See this link for details .

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  • $\begingroup$ The very successful Drude-Sommerfeld model is also known as the Free Electron Model, en.wikipedia.org/wiki/Free_electron_model . $\endgroup$
    – my2cts
    Commented Feb 18, 2020 at 20:02
  • $\begingroup$ The "free" is defined within ghe lattice, and it is a good approximation , The air about the lattice of a solid is not a lattice.. $\endgroup$
    – anna v
    Commented Feb 19, 2020 at 5:39
  • $\begingroup$ I took time to re-read your answer but I’m unable to understand the gist of it. Did you mean to say that electrons travel from metals to air and hence sparks were created? $\endgroup$
    – user240696
    Commented Feb 19, 2020 at 8:35

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