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The many faces of the microwave: cooks, radiates ... myths
The article discusses the design of the microwave oven and the mechanisms of heating food. The complete inconsistency of rumors about the harmful effects of microwaves on humans and products is shown.
Microwave ovens, or microwaves, quickly entered our everyday life. The hostesses quickly appreciated their convenience - a few tens of seconds, and warmed dishes can be served on the table. Culinary recipes, and even books focused on the use of a microwave oven, have become an exchange currency among home-cooks.
Immediately there were rumors about the extreme harmfulness of microwave ovens for food and housewives. The remedy was found almost immediately: “tested” on computer and TV monitors, cacti and other spiny representatives of the home flora migrated to the kitchens, protecting their housewives from the harmful effects of the new “miracle” of household electrical appliances.
Repeated assurances of manufacturers and experts about the complete safety of such products could not convince the fair sex, on whose shoulders lies the burden of providing the family with delicious food. There is no trust for husbands. Especially goes to those whose profession is related to electricity or technology.
After listening to the assurances of the complete harmlessness of the microwave, you are told in response that your girlfriend (option: friend of a friend) was read, or they were secretly told the shocking details of the harmful effects of the stove on a person or food.
It is useless to appeal to common sense and the opinion of official bodies in such cases. Common sense (not to be confused with practicality) is rarely present among our chosen ones. Apparently, when choosing a life partner, as a young man, this feature did not appear on the list of priority ones. Still, we will try to make an attempt to deal with the harmfulness of microwaves and, at the same time, check the truth of the proverb about smoke without fire.
The design and layout of the microwave is quite simple, which cannot be said about the mechanisms of propagation of microwave oscillations and their absorption by food.
The furnace consists of a high-voltage power source (transformer) and a magnetron - a generator of high-frequency oscillations. It is difficult to coordinate the magnetron radiation directly with the furnace volume; therefore, the oscillations of the generator are brought to the working volume of the furnace using a waveguide.
The purpose of the remaining elements for the topic of our conversation is not so important: this is a protective limit switch for locking the door, magnetron cooling fans, a mechanical or electronic timer, and a microwave power regulator. Furnaces operate at a frequency of 2450 MHz so as not to be aware of interference in the ranges of location stations and communication channels.
During the operation of the microwave oven, the oscillations are distributed unevenly throughout the volume; the heated products also have a complex shape. For uniform power take-off from the microwave path, a rotary platform is used in the furnaces, which is rotated by the engine.
Now let's see what are the chances of microwave radiation to leave the limits of the microwave. The furnace body is made of sheet metal coated with enamel (expensive models) or paint (budget stoves).
In the internal volume of the furnace, radiation propagates throughout the space in contact with the metal walls. In this case, eddy currents (Foucault) are induced in a thin layer of metal (less than 10 microns), which displace radiation from the metal volume. This phenomenon, known in radio engineering, is called the skin effect. Due to the skin effect, radiation has practically no chance to leave the furnace.
The front door is often made of heat-resistant glass, having: either a metal protective net, or a translucent conductive coating. Therefore, microwave radiation will also not be able to penetrate through the front door.
International sanitary standards for household high-frequency products are very stringent. The power of microwave radiation at a distance of 5 cm from the surface of furnaces should not exceed 5 milliwatts. Almost all high-frequency household products, including the cheapest, easily fit into this requirement.
Now about the dangers of food cooked in the microwave. The energy selection of high-frequency oscillations and their conversion into heat occurs in two ways. The first is the eddy currents and skin effect already mentioned above. Those products that contain a lot of water have a fairly high conductivity. The resulting eddy currents heat the food. But the penetration depth of microwave oscillations is limited to 5-15 mm. Deeper heating is due to conventional heat transfer.
Another mechanism is molecular heating. Many substances have a dipole moment (asymmetry of molecules). Amino acids, fats, proteins, and especially water, have a dipole molecular structure. Under the influence of external high frequency electromagnetic radiation, dipole molecules begin to move with a frequency of 2450 MHz, scattering field energy in the form of heat. But no destruction or splitting of the molecules occurs!
Therefore, horror stories about the dangers of cancer due to the appearance of active radicals (debris) of food molecules do not have the slightest foundation. Nutritionists, on the contrary, make a conclusion about the usefulness of cooking using microwave ovens. By taste and the amount of stored nutrients and vitamins, it is similar to steamed food.
So microwave ovens are completely safe to use? Of course not! They are dangerous, like any electrical appliance. Standard warnings for using microwave ovens are usually provided in the operating instructions. I would like to draw attention to only one feature that mistresses often neglect.
In no case should microwave ovens be turned on empty, or to heat food weighing less than 200-300 grams. In such cases, the life of the magnetron (the most expensive part of the stove) is sharply reduced. Manufacturers often stick an inscription on the stove: "Do not drive empty!" But, unfortunately, in English, therefore it is ignored. Otherwise, ovens are no more dangerous than conventional cooking devices. In conclusion, you enjoy your meal, and men - success on the thorny path of enlightening friends!
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