The invention of a microwave oven is the invention of a completely new method of cooking. In the 30s of the 20th century at the same time in different countries scientists were working on the production of high-power radio waves of a microwave band. These radio waves primarily intended to use with the radar. Quite by accident in 1932 two employees of one of the laboratories in the United States placed two sausages near a powerful microwave generator and roasted them. So a microwave oven was invented.
Microwaves with frequency 2450 MHz are uses in microwave ovens. Such frequency uses consistent with international agreements. It is necessary not to interfere with the radar and other devices that use microwaves.
High-voltage vacuum device (magnetron) is a source of microwaves. High voltage (3-4 kW) is supplied to a filament of the magnetron. Network voltage (220 V) is not enough for the magnetron, and it is powered by a special high-voltage transformer. Magnetrons power is about 700-850 watts. To cool the magnetron there is a fan that blows air over it. The fan also provides forced air convection in the oven chamber, so meals bake evenly.
Microwaves from the magnetron enter to the chamber of the oven through a special channel with metallic walls. The door also has a complex structure. It should provide an opportunity to review that is prepared in and don’t let microwaves get outside. This is multi-layered device made of glass or plastic plates. Between the plates there if a grid of perforated sheet metal. The metal reflects the microwaves back into the oven cavity, and the small slits (less than 3 mm) don’t let microwaves get outside.
Metal utensils are completely unsuitable for microwave cooking. Microwaves cannot penetrate through the metal, so they are reflected from it. This may cause an electric discharge (voltaic arc) and damage the oven. In addition, the reflected microwaves can pass through the glass door, which is not safe for health.
How do microwaves cook food?
To heat the food with micro waves it is necessary the presence of dipolar molecules. Such molecules have positive and negative electric charges. There are many such molecules in foods (molecules of fats, sugars and water). They are arranged in the direction of the electric field lines. While the direction of the field is reversed, the molecules immediately flipped through 180 degrees. It happens 4.9 billion times per second. So the molecules rotate at a breakneck speed and contact each other. As a result heat is generated, and it warms up food.
Water boils in a microwave oven not like in a kettle. This devise heats water simultaneously from all sides, and when the water will reach boiling point, the bubbles will not be formed. But if you put a metal spoon into the glass of water, it will suddenly seethe.
What you are forbidden to do
Never turn on the empty oven, without a single subject, which could absorb the microwaves. If the waves will not encounter with obstacles, they will be reflected by the walls of the oven. As a result the concentrated energy will be generated that can bring down the oven. It is necessary to put it in a glass of water as minimum.
Are microwaves dangerous or not?
Microwaves don’t impact on the biological tissues and food products.
Besides, microwave cooking requires a very small amount of fats, so such food is healthier and doesn’t represent any danger to humans.
Manufacturers provide strict measures to prevent the release of emitting to the outside. However, the direct effect of a microwave radiation emission can cause burns on the skin. But if you use such a device properly, the risk is completely absent.
Microwaves are attenuated in the atmosphere very quickly, and on the half a meter distance from the oven they become 100 times weaker. It is enough to move away from the oven at arm’s length, and you can feel safe.