Yes, that's why capacitor dielectrics are perfectly lossless, since they're far smaller than the operating wavelength! Ferrites have zero losses for the same reason!!
Wrong, of course.
Microwave heating (dielectric loss) doesn't suddenly fall to zero when the physical size
try putting some grape seeds in the middle some time...
Jamie
Yep. This is mostly just dielectric heating. Only AC e-field and resistiv ity inside the ant will matter. Treat everything as 2GHz capacitor plates with blobs of various dielectrics suspended between.
atio?
Bingo. Also, don't forget that the hot-spot antinodes are a quarter-wavel ength from any large conductor. In other words, the metal oven surfaces a re cold-spot nodes where the e-fields go to zero. If ants were up on food , they might get fried. The smart ones stay on the metal where the strong RF e-fields are mostly shorted out.
There's the "cockroach algorithm" in biology: run faster when conditions a re bad, stop when conditions are good. We'd expect the ants to randomly sc atter when the RF power turns on, then halt when they arrived at places whe re the RF field voltage is low.
Huh, possible ants experiment: cover a piece of cardboard with ants, and h ang it flat in the center of your microwave. (perhaps suspend with carbon fiber or other tiny threads.) Watch the ant distribution, then apply powe r. Wanna bet they instantly assemble into a "Chladni figure" of the RF no de pattern, with no ants at the antinodes? If they don't then you'd inste ad get a pattern of dead ants at the antinodes and live ones at the nodes.
Yep, it's just wrong. They're trying to prove that diathermy is impossible , since obviously the wavelength is so long compared to objects heated. A nd obviously no electrical device can work, since the spacing between wires is much smaller than the wavelength of the power supply.
Well, they do care. But look at it as capacitor plates driven at 2GHz, th en suspend various small hunks of dielectric between them. It's more a ma tter of Z-matching, since materials with zero ohms or zero mohs won't be he ated by the AC fields. Next, lower your drive freq to the industrial diath ermy bands. Water still gets hot, even though it's now 11 meters wavelengt h or far longer. But the overall current does fall with frequency (since it s a capacitor.) We'd have to crank up the RF voltage if we wanted the total heating to remain the same when frequency is lower.
I once boiled some water in a microwave, let it cool, boiled it again, and while boiling measured the surface temp with an IR pistol thermometer.
115C!!!With some work I probably could have got it much higher.
Need clean glassware to do it, and multiple boil/cool cycles to clean out a ll the microbubbles. Better wear a face shield. Some people report that nucleated boiling from superheated water can sound like a gunshot, and shat ters your glassware. It's a common occurrence with autoclave sterilizers. A local guy died from a glass shard penetrating his heart (but that was fr om superheated lavalamp water on a stovetop in a trailer park. Yeesh. Kee p your experiments in the garage, not trailer parks.)
It's rather hard to heat anything with DC if the load is inside a resonant microwave cavity. :)
Or in space at a given frequency, if it's not part of a resonant (or otherwise suitable) antenna, or...
If you happen to have a TEM0 mode (like coax, or any old wire -- a classical down-to-DC circuit), you get current flow at DC, but that heats resistive materials, not dielectric materials.
Microwave oven heating is a bit of both. Most metals are too conductive (R
They heat, all right, but ants move fastest when warm, so they all diffuse OUT of hot spots, and slow only when they get to a node (local microwave minimum). At a node, there's little heat.
All the metal walls of a microwave oven are nodes.
There may be an effect from dielectric heating of some capacitor, but the frequency of microwaves in an oven were chosen because water strongly absorbs it... directly.
-- Rick
Fascinating. Can ants be P- and N-doped? Can we make a very large, very slow, macroscopic, ant-approximated semiconductor diode?
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
Observation: They dont have any problems being on the rotating glass plate, thats well away from the nodes caused by metal surfaces. They dont like being on the food though, but thats because the food is hot.
Theory: I see the point about dielectric losses, but I guess the ants can get rid of enough energy that it does not bother them. Similar arguments probably apply to an aerosol of bacteria.
On Thu, 24 Dec 2015 16:06:08 -0800 (PST), Bill Beaty Gave us:
When they are IN the tupperware. (and only on the vertical surfaces, not on the floor of the tub) When they are on the grounded metal microwave interior wall, they stay room temp. Explain that, near field physical reality boy.
On Thu, 24 Dec 2015 23:12:29 -0600, "Tim Williams" Gave us:
Do they move faster or slower than the electron one pushes into a wire? I know another one comes out the other end, but it isn't the one you 'inserted'.
How long does a photon generated near the middle of the sun take to reach its surface and 'radiate away'?
On Fri, 25 Dec 2015 16:14:28 +1000, Adrian Jansen Gave us:
If anything suspended in the gasses in a microwave got heated, then the steam rising off of a dish coming up to temp in the oven would form turbulent movements, not merely rise slowly as they do.
How can you tell? All electrons look alike to me.
What is the sound of one hand clapping?
-- Rick
On Fri, 25 Dec 2015 02:29:30 -0500, rickman Gave us:
It is a known fact that electrons move through a conductor at slower than light speeds. The electron one pushes in is not the one the pops out the other end.
On Fri, 25 Dec 2015 02:29:30 -0500, rickman Gave us:
Always a retarded response, or are you just trying to get a notch further down on the totem pole than some of the other dolts here?
You still haven't explained how you tell one electron from another. If you can't tell the difference, how can it possibly matter?
-- Rick
On a sunny day (Thu, 24 Dec 2015 16:51:37 -0800 (PST)) it happened Bill Beaty wrote in :
Normally water will evaporate, you get steam, the thing boils dry, and your microwave may die from lack of load, mine actually has some clickson that does come in to protect the transformer. Then it won't work for many many minutes.
BTW I _always_ boil water in the microwave, sometimes for several minutes. The glassware is whatsit (goes to kitchen and looks): 'Arcuisine' (French I think). Had that (1 liter container) for about 15 years...
What does happens is chalk setting down, so you need to clean it after boiling.
I make Spaghetti in it, first boil, then spaghetti in it, set to 30% and leave for 18 or 19 minutes USE STRAINER :-) LOL.
Actually I also make rice, same procedure, but for brown rice 45 minutes. It is dry when ready, The ratio water / rice / time is critical. I guess anything is dangerous, you can slip on a banana peel too and die. Talking about boiling, we have the warmest winter ever recorded here, no white Christmas, more like +10 C. Plants get confused, grass starts growing, my plant makes a new leave, and bird no longer fly south.
So give it some time and leave you water outside, I understood the sun will engulf the earth 'later on;, so that should work, Today I am going to boil an other egg on the inductive heater.
On a sunny day (Thu, 24 Dec 2015 16:06:08 -0800 (PST)) it happened Bill Beaty wrote in :
You got a point there, was it not something to do with electron spins and resonance?
On Fri, 25 Dec 2015 07:58:15 GMT, Jan Panteltje Gave us:
The heating is done by hysteresis. The molecules toggle and the toggling causes heat due to friction.
There was a Navy demo where a person would place a grapefruit on the end of a sharpened broomstick and place it in front of a microwave dish, and it would explode pretty quickly. The demo was to illustrate why personnel were supposed to be sure and NOT walk in front of microwave dishes.
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