The principle of operation of the microwave oven: circuits, frequency and video

How exactly does a microwave work? What causes food, water and other substances to heat up, while the air or glass in the microwave almost does not heat up? How to handle a microwave so as not to spoil it and the cooked dish? You will find answers to these questions in our article!

The principle of operation of the microwave

The correct full name for a microwave is a microwave oven. Inside it (behind the dashboard) there is a special device for emitting radio waves - a magnetron, which can be seen from the diagram:

When a magnetron is operating, the electromagnetic waves emitted by it at a certain frequency cause the dipole molecules inside the furnace to oscillate at the same frequency. The most common dipole molecule in nature is a water molecule (in products - more fats and sugars). At the molecular level, a high vibrational frequency turns into an increase in temperature, so any products with a high water content quickly heat up. If there are very few or no water molecules inside the products (or materials) at all, heating almost does not occur.

The penetration depth of microwaves is small - 2-3 centimeters, however, the surface of the cooked microwave dish pierce easily, and in depth they meet the resistance of water molecules, so the product actually warms up from the inside.

To heat the products evenly, several approaches are used:

• Heat-resistant glass disc at the bottom of the microwave. It rotates with the dish, substituting all its sides under the radiation of the magnetron.
• Microwave. They are fed through a special waveguide (wide tube) from the magnetron to a rotating reflector, usually located in the upper part of the microwave oven. These microwave ovens can be used to heat still meals of large size and weight.

There are also so-called inverter microwave ovens. They differ from conventional models in that the magnetron operates continuously, but with reduced power consumption. This is achieved through the use of a so-called inverter (DC / AC converter) in the furnace instead of a traditional transformer.

In many microwave models, the magnetron is covered with a special translucent plate. It is transparent to microwave radiation, but does not allow steam, splashes of fat and other foreign substances to enter the microwave through an opening in the shielding. Do not remove this plate, and if it is required for cleaning from grease, then after complete drying, be sure to return it to its place.

Look for all about microwave cleaning in this article: https://sovetexpert.ru/chistka-mikrovolnovoj-pechi.html.

Despite popular belief, microwave radiation does not kill germs. At least, this is not scientifically proven. On the other hand, the complex effect of high temperature and microwaves on water molecules inside bacteria and viruses during A few minutes reduces their number many times, and with those that remain, your immune system can cope on its own.

Microwave Frequency

Most magnetrons emit waves at a frequency of 2450 MHz (megahertz, or millions of oscillations per second). These are decimeter wavelengths (12.25 cm long). Some industrial plants, for example in the USA, operate at 915 MHz. Forced vibrations of water molecules are not resonant vibrations, since for them the resonant frequency is an order of magnitude higher - 22.24 GHz (gigahertz, or billions of vibrations per second).

It is not necessary to be afraid of harmful radiation from the microwave. The first mass production of microwaves was made in Japan by Sharp in 1962. Since then, many years have passed, tens of millions of Japanese people have been heating food in microwave ovens for decades and the average life expectancy of the Japanese is the envy of the whole world.

How does a microwave grill work?

The grill allows you to fry food in a microwave oven using ordinary heat rather than microwaves. It is she who makes an appetizing crust on dishes, which does not appear during ordinary microwave processing.

The grill spiral is in the upper part of the furnace and there are two types:

• TENY (heat electric heaters). TEN is a metal tube, inside of which there is a thin spiral made of an alloy of nickel and chromium. A current passes through the spiral, and it heats up.
• Quartz. A quartz grill is also a heating element, only instead of a metal tube there is a glass shell, between the spiral and the tube is insulating quartz sand.

There are designs of microwave ovens with grill and convection. Convection is simply blowing hot food into your dish during cooking. For such blowing, a fan is installed in the microwave, blowing off the heated air from the grill spiral to the side of the dish.

Most microwave models allow you to use both TEN and microwave at the same time. However, keep in mind that such a combination can greatly heat the outlet and wires in your room.

Read the following article about the principles of choosing a microwave oven for your needs: https://sovetexpert.ru/kakuyu-kupit-mikrovolnovku.html.

Microwave Instructions

To properly handle your microwave, you need to carefully approach all points - from the choice of dishes to the correct shutdown after use.

What utensils to use?

The best material for heating in the microwave is heat-resistant glassware. Porcelain and other ceramic products, paper (cardboard) are also well suited. Microwaves pass through them very easily and hardly heat them. But the dishes from the following materials must be discarded:

• Plastic. It passes microwave radiation well, but due to toxic components in the manufacture (for example, polystyrene foam) it can be a danger to your health.
• Metal. They conduct electric current without passing microwaves. So to cook or just warm the dish in an aluminum pan or cast-iron pot does not work. The metal simply will not let electromagnetic waves pass through to the products and they will remain cold. In this case, the metal itself, of course, will heat up, and products can also be heated from its heat. But this can lead to a breakdown of the microwave oven, and it will take a long time to wait for the preparation of the dish. Read microwave repair instructions here.

• Melamine. This is a light and beautiful material for dishes, similar to porcelain, but it can not be placed in a microwave oven. The fact is that when heated, it releases toxins that are dangerous to your health.

As for the shape of the dishes, it can be anything, but not with a narrow neck, because when used for heating in a microwave, it can be dangerous. The fact is that some liquids are heated to the boiling point, but vigorous mixing inside the volume does not occur. But when you take out such a jug or flask from the microwave oven, the liquid will instantly boil, boiling foam will pour out of the container, and you can get a burn. For example, distilled water and some refined oils of plant origin behave under certain conditions.

We recommend reading the article on what utensils are suitable for microwave.

Proper product handling

Initially, it is worthwhile to accurately determine what you can not defrost in the microwave:

• Butter. If you put it in the microwave and leave for a long time, it will not just melt, but also boil, staining the entire oven from the inside. This happens because inside the oil there is not only the oil itself, but also water. It boils at 100 degrees, and the oil at about 120. So the water can turn into steam before the oil melts, and water vapor will spread the oil throughout the stove.

• Dense Shell Products. For example, these are eggs, tomatoes, whole bird liver. When heated, some of the water does not just gradually heat up, but immediately turns into steam. If you heat food for a long time, even more steam is formed from direct heating. This pair has nowhere to go, so the pressure inside the tank rises and leads to an explosion.
• Hermetically sealed dishes. For example, canned food and bottles. The reason is the same as in the previous paragraphs - the probability of an explosion is high.

Further, it is worth taking tips on how to handle food properly when heating or microwave cooking:

• Sausages, tightly packed in a shell, before microwave heating must be pierced with a fork to create holes for steam to escape, otherwise it will turn the sausages from the inside.
• In eggs and other products, it is necessary to destroy all external and internal membranes, for example, make an omelet or cut the liver.
• For cooking eggs and other products in the microwave, special shielding pans are used. Water is poured into it, it is heated from microwave waves, and electromagnetic radiation does not reach the eggs - they are covered by a screen.
• If a small dish is placed in the microwave, add an ordinary glass of water to it. So you will avoid overheating of the magnetron.
• It is better to salt any liquid dishes in the microwave in advance, and not after cooking. So you save time and energy. The fact is that distilled (unsalted) water in the microwave is heated and boils, but longer than ordinary water.
• A very frozen product (meat, for example) will be defrosted in the microwave for a long time, and you need to turn on the microwave oven at minimum power. The reason is that ice molecules are not water molecules, microwave waves do not shake them so intensely. In addition, ice molecules form a rather rigid structure and it is not so easy to “swing” them as water molecules.

Dry bread is often recommended to “soften” in the microwave, but it can catch fire with prolonged exposure and maximum microwave power. The same can happen even with popcorn, designed for cooking in the microwave. Therefore, when such products are placed in the microwave, you need to be vigilant.

On / Off Rules

You can not turn on an empty microwave, especially at full power:

1. Inside the oven, all the walls (and even the door) are a special metallized screen that reflects microwaves back into the microwave. The only place where there is no screen is the hole for the exit of electromagnetic waves from the magnetron.
2. When there are products on the pallet, microwaves consume their energy to heat these products. If there is nothing to absorb energy, microwave radiation is reflected from the walls of the shielding surfaces, while the wave density increases more and more.
3. Microwave radiation falls back into the magnetron, and if it consists of metal, it simply overheats and can fail.

It is believed that after heating the food in a microwave oven, it is better to let it stand for 3-5 minutes. Then the so-called "free radicals" have time to neutralize, that is, parts of molecules that have decayed into parts under the influence of microwaves.

Video: How does the microwave work?

All of the above about the principle of operation of the device is well illustrated in the following video:

After reading our article, you have become much better at understanding the principle of operation of the microwave oven. Now you know what it can do better than a conventional oven and electric stove, and what it cannot, and what actions are generally unacceptable when working with a microwave.