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The science behind nuking that TV dinner
October 30, 2008 | 15
Water molecules exist in most foods. They have positive and negative charge at opposite “ends.” The electric field of a microwave orients the positive ends in one direction, but the field reverses 4.9 billion times a second, causing the molecules to turn back and forth....[More]
Transformer, diode and capacitor raise household electricity from 120 to 3,000 volts or more and deliver it through a wire to a magnetron. The magnetron generates microwaves, sent by an antenna through a waveguide into the cooking chamber, where the waves reflect off metal walls....[More]
High voltage is sent to the cathode filament. After it heats up, it emits electrons that the positively charged anode plates attract. The attached antenna resonates at 2.45 gigahertz and emits microwaves from its tip--just like a radio-transmission antenna....[More]
Large magnets impose a field that causes the outward-flowing cloud to revolve ( left ). As it does, it forms spokes that pass each cavity between the plates ( right )....[More]
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15 Comments
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Reply | Report Abuse | Link to thisMy microwave makes my wifi connection die completely anywhere in the house.
Reply | Report Abuse | Link to thisI thought the cooking from within was a myth. That it cooks from the outside like everything else.
Reply | Report Abuse | Link to thisWell maybe if the article said something about water molecules and resonance then we would all know. I think it is ironic that the title is "How a microwave oven works". It should be : "We think we heard in Prevention that microwaes don't deplete nutrients from food".
Reply | Report Abuse | Link to thisOf course it depletes nutrients and vitamins. Our living conditions and our environment are filled with health problems. You're reheating food here. Once you cook it, you reheat it! It doesn't taste exactly the same. There must be alot of people out there that must know that rehating food causes cancer.
Reply | Report Abuse | Link to thisA couple of years back I was experimenting with Wifi. I wanted to find a way to reliably attenuate the signal at close distance. To try this out I put a cordless phone inside a one litre aluminium container and that inside a bigger one. I then put this lot inside the microwave oven and closed the door. I called myself on that phone and the phone still rang, in spite of two layers of metal plus the microwave door. Why?
Reply | Report Abuse | Link to thisCooking/heating in any form will tend to alter the original state of any food and thus possibly deplete some of the nutrients. But CANCER? Oh really - By what mechanism will simply heating make a food cancerous?
Reply | Report Abuse | Link to thisDoes that mean that eating in a warm house is more dangerous than eating outside (if its cool out)???
Granted, supplying enough energy with the right substances present, can induce chemical reactions. But that is the very reason that this form of heating food can be the safest. The most energy is applied INside, where no foreign substances should be. Furthermore, the amount of energy used can be much less producing fewer chemical reactions.
I believe that at a short distance the effect was due to the near-field condition. Close to the transmitting antenna, the magnetic field is decoupled to the electric field, and would get to the receiver. The microwave shielding would only block an electromagnetic far-field wave.
Reply | Report Abuse | Link to thisFirst, the microwave door has a 1/4 shorted stub built in where it overlaps the door frame which blocks leakage near the magnetron's output frequency. The tuned gap is not effective at most other frequencies, leaving the door to act as a slotted antenna and let the cordless signal through. There are 4 widely different bands in use for cordless phones and there are several different wifi bands. Careful measurements would be affected by the bands chosen for the experiment.
Reply | Report Abuse | Link to thisSecond, did the aluminum container have a tightly fitting aluminum lid? Aluminum always has an insulating oxide layer that must be broken through each time the necessary electrical contact is to be made. A good connection all around the lid should have blocked the signal completely in your test.
Finally every implementation of shielding I've ever tested has resulted in large error bars. There are so many confounding factors that influence the results. Reflections, impedance mismatches, non-ideal test antennas, all make this a frustrating field to gather repeatable results.
Jofez, I generally don't hate my food at all. Even if I hated my food I doubt I would change my mind, not once but twice and "rehate" my food.
Reply | Report Abuse | Link to thisOddly enough, while reheating (notice the spelling) does have a negative affect on nutrition, I have never seen anything indicating a link to cancer although cooking fats increased saturated fat levels. Hate, however, stresses the body and weakens the immune system so maybe that actually would matter.
Contrary to what the article claims, it is possible to heat both dry ceramics and dry glass with microwaves. This is a standard way of taking the chill off cold plates taken from an uninsulated cabinet in wintertime. Apparantly the shape of silica and alumina molecules are similar enough to water that they oscillate at microwave frequencies.
Reply | Report Abuse | Link to thisWhile we're on the subject, why does the oven need a magnetron to generate 2.45 ghz, when my cell phone produces the same frequency without one? Why not just scale up a cell phone oscillator to the desired output power level and do away with the magnetron magnet and related parts?
Reply | Report Abuse | Link to thisIs there moving parts in the magnetron, or all is created by only electric current passing through?
Reply | Report Abuse | Link to thisThen get a new microwave.
Reply | Report Abuse | Link to thisI can understand that if nutrients are removed (by the way, it is very easy to lose water-soluble nutrients) that you lose many chemo-protective mechanisms for protection against cancer. But reheating having a causal link - I am not so sure. Possibility, of course. But do you have anything scientific?
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