If we are told not to put metal into microwave ovens, why is there a metal plate fixed in the oven already?
537697
Good question. Is it real metal though?
39938
They're generally safe to use. But recently, there was an article about using foam and plastics in a microwave. The point was that glass is much safer in the microwave. Plastics are best for the fridge or freezer.
951487
A microwave oven heats food by bombarding it with Microwave energy (a portion of the electromagnetic spectrum, much like visible light or radio waves).  When water molecules are hit by a photons in the microwave frequency, they become excited, and move around faster - this is what causes them to heat up.\n\nSince the outer surfaces of the food are the ones exposed to the most microwaves, they tend to heat up faster than the insides.\n\nBasically, for a microwave to excite a molecule on the inside, it has to 'miss' all the molecules on the outside to get to it.  The thicker your food is, the less likely that is to happen.\n\nWhat ends up happening is that the outside of the food gets heated by direct radiation, while the inside has to be heated by conduction - the transfer of heat from the outer surfaces to the inner ones directly.  This process is much slower, and so you end up with food that is hot on the outside, and cold on the inside.\n\n\nThat was longer than I anticipated, but hopefully it helps!
756976
The magnetron generates electromagnetic waves. The food particals- absorb the energy and start viberating faster. So food heats up, and gets cooked. Glass and ceramic does not absorbe the energy to the same extent so remains relatively cool.
589671
Microvaves are very short radio waves and will "transmit" through any hole you make in a microwave oven.  The waves can denature (cook) human flesh and are highly dangerous.  Even faulty door seals were a problem in early microwave ovens and it was feared they might ruin eye sight.  You should not alter any microwave oven unless you are a microwave engineer with special leak detection equipment.
141111
Its like a microwave for metals, only kilohertz instead of gigahertz.  Its done with a coil instead of a magnetron.
1085489
Metal objects such as the spoon & the pointed ends of the fork act to concentrate the electric field formed at the tips. This has the effect of exceeding the dielectric breakdown gradient of air, about 3 megavolts per meter (3×106V/m), causing sparks to form. This effect is somewhat analogous to the effect of St. Elmo's fire.\nMetal or conductive object placed into the microwave will act as an antenna, and its electrons will thus be thrashed back and forth through the object (a high frequency alternating current) causing some ohmic heating to occur\n\n- no damage to magnetron, but !
976128
I believe the answer is conductive.  This is the process in which things are silver plated.  \n\nHere's how it goes.You fill a tray that has been lined with aluminum foil with salt water ( or is it plain water ? ).  You run a current through the aluminum foil.  The electrons in the the foil get excited due to the electrical current and start releasing aluminum ions ( Al-, I think )  Now, take your rusty, dull ' silver ' spoon.  Place it in the bath for about 2 hours.  Be careful,  electricity, water and living things don't mix well.  After 2 hours, remove the electrical current source and remove the spoon.  The free ions in the water would have coated the spoon, making it shining again.\n\nActually, toothpaste to clean the spoon is easier.
20070
Cooking food with microwaves was discovered by Percy Spencer while building magnetrons for radar sets at Raytheon. He was working on an active radar set when he noticed a strange sensation, and saw that a chocolate bar he had in his pocket had melted.\n\nIt was patented in 1946
344110
The website TruthorFiction decided this is not true.\n\n"Don't Use Plastic for Heating Foods in a Microwave Oven Because of Exposure to Dioxins-Unproven! & Fiction!"\n\nThis site does an exhaustive investigation regarding "rumors" put out there.  You can read how they came to this conclusion at the following site:\n\nhttp://www.truthorfiction.com/rumors/d/dioxins.htm
163211
Build a Faraday cage.  A Faraday cage is a grounded metal structure...basically a metal box...that prevents electric fields from getting inside.  Microwave ovens are a kind of Faraday cage, if they weren't we might get cooked instead of our food.
999979
The signal from the satellite is a microwave signal of a little more than a centimeter in wavelength. That means they will not pass through any metal with a hole smaller than that dimension, but instead are reflected. Microwaves are reflected from metal very much like light is reflected from metals. The satellite dish that appears to be plastic or fiberglass actually has metal embedded within it. Any type of metal, including copper, will work. The metal most commonly used is aluminum or steel.\n\nThe metal mesh is not used because of its conductive properties. Its conductivity is irrelevant. It is acting as a reflector and because of the parabolic shape of the dish is reflecting the signal in concentrated form into the receiver that sets over the front of the dish. \n\nI seriously doubt that any satellite dishes have silver in them, and using copper would be a waste of money, since copper is much more expensive than steel or aluminum. It is even possible to build a satellite dish out of chicken wire or screen wire. The wire is close enough together to reflect the microwaves. However, the shape is critical, and the plastic or fiberglass is designed to keep the critical shape. \n\nHere are some diagrams:\nhttp://www.mlesat.com/antennas.html\nThe microwave spectrum (in centimeters):\nhttp://meted.ucar.edu/npoess/microwave_topics/overview/print.htm#s1p2\nManufacture of dishes:\nhttp://www.madehow.com/Volume-1/Satellite-Dish.html
8081
The short answer is: Microwaves bombard the metal with radio waves (electrons). Where that energy builds up, it can build to the point the energy will arc to another spot. Works great with crumpled foil, or CD-ROM's you don't want to use anymore. Quoth Wikipedia: "... the pointed ends of the fork will act to concentrate the electric field formed at the tips. This has the effect of exceeding the dielectric breakdown gradient of air, about 3 megavolts per meter (3×106V/m), causing sparks to form. This effect is directly analogous to the effect of St. Elmo's fire."\n\nP.S. According to Mythbusters, you CANNOT damage your microwave by putting metal objects in it for short periods of time. You would have to microwave metal a LOT for it to overload the magnetron and cause damage (most magnetrons in consumer microwaves have overload protection anyway). Try microwaving a CD you don't need anymore upside-down in your microwave for 2-5 seconds, and watch the miracle of radio lithography (just don't do it to the point the plastic melts, or who knows what kind of toxic fumes you might release from the plastic).
60247
Health problems usually associated with electromagnetic radiation (such as cancer) are caused by waves of much higher frequency.  In fact, the light from an ordinary 100-watt light bulb or the heats from a campfire (the heat only not including the smoke) have greater potential to cause cancer.  The only health problem that a microwave could cause is burns, but unless you really do break the glass on your microwave, you should be fine, just be careful about burning yourself on hot dishes and plates.
1026790
When you microwave things you let off electro-magnetic radiation. That is why you want to check the seal on your microwave occasionally because if this leaks it is very harmful. Microwave radiation puts you at risk for cancer.\n\nTen reasons to throw out your Microwave oven (taken from research): \n\n1. Continually eating food processed from a microwave oven causes long term, permanent, brain damage by ‘shorting out” electrical impulses in the brain (de-polarizing or de-magnetizing the brain tissue).\n2. The human body cannot metabolize (breakdown) the unknown by-products created in microwaved food.\n3. Male and female hormone production is shut down and/or altered by continually eating microwaved foods.\n4. The effects of microwaved food by-products are residual (long term, permanent) within the human body.\n5. Minerals, vitamins, and nutrients of all microwaved food is reduced or altered so that the human body gets little or no benefit, or the human body absorbs altered compounds that cannot be broken down.\n6. The minerals in vegetables are altered into cancerous free radicals when cooked in microwave ovens.\n7. Microwaved foods cause stomach and intestinal cancerous growths (tumors). This may explain the rapid increased rate of colon cancer in America.\n8. The prolonged eating of microwaved foods causes cancerous cells to increase in human blood.\n9. Continual ingestion of microwaved food causes immune system deficiencies through lymph gland and serum alterations.\n10. Eating microwaved food causes loss of memory, concentration, emotional instability, and a decrease of intelligence.
621371
It is to stop reactions with organic products when cooking food. Brass is the term used for alloys of copper and zinc in a solid solution. It is more than 50% copper and from 5 to 20% zinc, in comparison to bronze which is principally an alloy of copper and tin. The copper in the alloy reacts with organic acids in the foodstuffs that can lead to food poisoning. The tin stops that from happening.
995260
These things are called "microwave susceptors".  They are made up of a material (typically a metal like aluminum flakes) that strongly absorbs microwave radiation.  This materials is embedded in a heat-resistant polymer and coated as a thin film on a part of the packaging.  \n\nDo a search for "microwave susceptor" on  your favorite search engine and you'll get lots of hits from manufacturers of these things.