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InteractiveMindFlag for United Kingdom of Great Britain and Northern Ireland asked on

Candle in a microwave. Plasma?

This is what happens when you put a candle in a microwave:
http://uk.youtube.com/watch?v=r6PPq8GwZgU

What is the physics behind this? What's actually happening? And why does it go blue at one point? It's really blue-hot?!
Math / Science

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afoong1

8/22/2022 - Mon
RohitBagchi

Good find there ;)

You may want to check this out : http://amasci.com/weird/microwave/voltage2.html

Cheers!
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aburr

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0av067

I believe that once they shut the door to the microwave they allow the carbon from the smoke of the burning candles build up and heat up until it reaches a point where it can conduct and therefore begin to absorb EMF (microwave in this case).  Once this happens the carbon cloud glows.  I would guess that this phenomenon occurs right above the flame of the candles because that is where the carbon in the smoke is most dense and the heat from the candle can contribute the most thermal energy (which would help the carbon reach conduction).
I would imagine that aburr is correct in regards to the blue color.  I would guess that it is the same reason why sparks are blue: the heat or free electrons colide with nitrogen in the air, allowing electrons in the nitrogen to become excited and subsequently become reabsorbed by their parent atoms, which results in the emission of a blue wavelength photon.
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0av067

I believe the same phenomenon that was described earlier can occur with simply pencil lead (which is carbon in the form of graphite).

http://www.youtube.com/watch?v=lo5GsOZAgsk
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fblack61
aleghart

It's not the same.  Paraffin wax vapors burn with the presence of a flame.

Graphite, like other electrically conductive materials, is throwing ions.

You can put lots of metal in a microwave (I frequently do while heating and cooking foods).  Works fine until you give it an unstable edge.  Then, ions will be thrown off and electrical discharge will show as blue sparks.

You can see the discharge patterns in a CD.  They appear as lightning forks after about 5 seconds on full power.
0av067

You raise a good distinction aleghart.  However, I believe, both phenomenon are occurring with the candle in the microwave!  Here's why:
The wax in a candle is an insulator and also will not resonate at the frequency of microwave radiation; in other words, microwaves cannot heat candle wax and therefore will not vaporize and produce the flame that you are seeing.  Instead, the carbon in the smoke is what conducts the microwave radiation initially, forming a very hot cloud right around the flame and wax.  The heat from this cloud is what heats up the wax, causing it to vaporize and combust, alongside the ionizing gas in the carbon cloud above the candle.  This would better explain why, in the video, we see a yellow flame as well as blue light, similar to the graphite video, as well as why we hear a zapping noise everytime the flame cloud appears.
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rid

I'm in with 0av067 on this one; the flames (and involved gasses/molecules in a transitional state) are conductive to electricity, as thery're partly ionized. That should explain the flares and the "power-surge-sound" from the oven. Ordinary combustion made easy by added heat and partly vaporized oil is of course also involved.
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rid

Candles give off soot = carbon, no doubt. The carbon particles are glowing from the reaction with oxygen = they're partly ionized (during the process). Some conductivity inside the flame is probable and I think I've seen other experiments on that, but I can't find the references just now. They were pre-youtube anyway, so there are no movies; I think it was about using flames as sound-emitting objects by running a current through them.
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d-glitch

0av067

What makes me hesitant to say that the action does not involve carbon conduction of EMR is for two reasons: first, if there is only super heated water vapor there is no explanation for the blue light or the buzzing sound.  Both can be seen and heard quite well in the candle and matchstick film (the blue light especially towards the end of the matchstick film).  Second, in the burning toothpick example, there is no wax vapor as in the first video but we still see the same phenomenon.  I'm not saying that there is no burning wax in the initial video, just that there should be something more than vapor and wax.  I don't get how the super hot vapor would produce the floating, buzzing, purple-blue glow.

I think a good experiment to eliminate my carbon conduction idea would be to put a wet toothpick in the microwave and see what results (although this eliminates other chemicals that the water vapor can react with like carbon dioxide etc.).
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InteractiveMind

Very interesting so far.

"If you fill a small barrel with oil and set it alight it will burn quiety. If you then throw in a glass of water it will explode"

Why does this happen? I remember being shown this at 'Hazard Alley' as a kid; they threw a glass of water on a chip pan fire, and woooosh--scary. It's the same thing I suppose. Why does this happen though? Something to do with the oxygen in the water? Or what?


Thanks so far
d-glitch

No.  The oil is very hot, like 350 deg C, so the water boils violently and atomizes the oil.
(Atomize is little droplets, not atoms.)
Little droplets have lots of surface area and easy access to oxygen in the air.

Just like a hair spray flame thrower.
d-glitch

>>  The oil is very hot, like 350 deg C,

That should be 350 deg F (174 C).  Still plenty hot enough for violent boiling.
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afoong1

plasma burns hotter than light (924 degrees K)
so if you take the opposite of that -924 dK, you get lower than absolute zero.
absolute zero is pretty much the boss of anything temperature related, so 924, retranslates to 256 dK.

256 is 6 more than 250.
planck's constant is 250

what is 6 then?

well, you have a candle, correct?
is it larger or smaller than 6 cm?

cut your candle in half.

is it larger or smaller than 6 cm?

cut it in half until the candle is larger or smaller than 6 cm.

place largest candle in the microwave.

microwave on high for 20 seconds

you should be able to SEE a force of 12 = ma

the accelleration will be inversely proportional to the formula, if manipulated properly

after microwaving the largest candle, soak in pure unfiiltered water overnight (this absorbs the most h20 molecules, the key component in plasma)

microwave on high again after lighting, and the candle will evaporate and resolidify into solid plasma (great on toast)