What determines the frequency of arc currents when arcs occur inside a microwave oven?
October 26, 2012 7:42 PM Subscribe
What determines the frequency of the arc current when an arc occurs inside a microwave oven?
posted by Juffo-Wup to technology (7 answers total) 4 users marked this as a favorite
Earlier this evening, I put a 6 oz metal, mostly empty, tomato paste can (along with some other items) in my microwave oven as part of an experiment. When I turned the microwave on, an arc formed, seemingly across the diameter of the open top of the can.
Although I quickly shut the oven off once the arcing started, I noticed that the arc made a distinctive sound with a relatively low frequency; I would say well under 100 Hz.
This made me wonder what determines the frequency of the arc currents caused by a microwave. The microwave oven itself emits RF around 2.4 GHz, but the sound I heard was, obviously, well below that. I'm guessing perhaps it has something to do with the conductivity of the metal and the distance involved, but I would like to hear from someone who actually knows or has some sound ideas.
Also, for what it's worth, why did the can start arcing in the first place? I would have expected it not to, given the can's relatively rounded top edge. I would have expected current to be induced to flow throughout the can as opposed to arcing across its top (open) surface. Any explanations of that are welcome as well.