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Re: Ball lightning - Terry's thoughts....

Original poster: Scott Stephens <scottxs@xxxxxxxxxxx>

Tesla list wrote:

some physics student claimed that microwave ovens couldn't produce corona,
since 500 watts RF doesn't give a wave with a high enough voltage to
trigger sparks. Ah, but what if we aren't cooking a roast? What if we
have a high-Q resonant waveguide? In that case we might only inject
500watts... but inside the waveguide we'd have 100.5 kilowatts going out,
and 100 kilowatts bouncing back again, creating an immense standing wave
and huge electric currents in the ground connection, but with only
500watts being absorbed in the conductors.


Two things to consider before you discount what your physics student:

1. The amount of resonant voltage increase depends on the loss (often derivable from the Q) of the cavity.

2. The impedance, moreover the capacitance of the waveguide will determine the impedance and voltage at a given power level.

So:

1. What is the impedance of a microwave oven cavity?
2. What is the Q of that cavity?

MO frequencies are 2 to 3 orders of magnitude higher than TC frequencies. For comparable Q's, (IIRC single-mode waveguide filters have Q's in the 100's) I'll SWAG the resonant voltage increase might be 10 to 30 times the nominal value, up to perhaps 1000 volts. Not enough for corona in air. Superconductive filters for 800 MHz cell phones might have Q's 10,000 - 100,000, IIRC.

Since MO plasmas usually require a conductive carbon or metal, or ionization from the short UV from an external arc source, I suspect your physics student is right about kWatt-class MO's inability to ignite a plasma in air, even if argon. Perhaps somebody should do some math?

Scott