How does the microwave oven work?

A microwave can cook super fast food or heat cold food in just a minute or less. But how does this great invention work? In this article, we will discover the science behind one of the revolutionary home appliances of the 20th century.

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Microwave (microwave) is a form of energy

Microwave waves (microwaves) are a type of electromagnetic waves that can travel through space at the speed of light. We cannot see the microwaves, but if possible, we will see inside the microwave when cooking is bright like a headlight.

Microwave waves have shorter wavelengths than radio waves but are longer than infrared rays. The type of microwave commonly used for cooking has a wavelength of about 12cm. With such a length, microwaves can be absorbed by most foods. But microwaves, known as photons, do not have enough energy to destroy molecules and cause cancers like ultraviolet or X-rays.

Electromagnetic wave ladder

Microwave

Inside the microwave there is a part called a magnetron . It is an electromagnetic control tube, which helps turn electricity into microwaves. To power the magnetron, the microwave has a transformer with the function of changing the indoor current with a voltage of 120V / 220V up to a voltage of 4000V or higher. This voltage heats the filament in the middle of the magnetron, causing electrons to fire.

The electron fires when the filament is heated

The electrons will fire in a straight line to an a note, or anode, surrounding the filament, but the two magnets above and below the note will break the electron back to the filament and cause them to follow. circle.

The magnet bends the flow of electrons back

The microwaves will be emitted when electrons sweep through the holes in a note.

The recesses on the circular nodules produce microwaves when electrons flow through them

It was like blowing a breath across the mouth of a glass bottle. But instead of creating whistles because of the frequency change, here the oscillating waves will be emitted at a certain frequency, usually around 2.45GHz. The generated microwaves will be transmitted to the cooking chamber by an antenna. There they will move back and forth to seep into food.

At the microwave door there is a metal grid that can reflect microwave waves like a mirror and keep it from being leaked out. This mesh eye is small enough so that the microwaves cannot escape but are large enough for light to pass through, so that the food being cooked can be seen.

Almost all microwaves have a glass turntable to spin the food, so that the heat is evenly distributed. If you don't move like that, your food will live where you are.

How do microwaves cook food?

When we press the start button, it usually takes only 2 seconds for the microwave to heat the filament inside the magnetron tube. The microwaves produced will then be blown into the cooking chamber.

With a normal frequency of 2.45GHZ, microwaves are easily absorbed by water, fat and sugar. The waves inside the oven will be transmitted at the right frequency so that they can go deep into the food and transmit most of the energy to the amount of water inside the food. Low water solids hardly absorb microwaves. That's why microwave-exclusive containers don't heat up like food inside it.

Microwave waves heat food by rotating water molecules back and forth. These molecules have a negatively charged head and a positively charged head. A single water molecule is shaped like a Mickey Mouse's head. You can imagine that negatively charged oxygen molecules are Mickey's face, and two positively charged small hydrogen molecules are his ears.

The positive charge of the water molecule always tries to follow the microwave's electric field, while the negatively charged head is pointing in the opposite direction. But because the electric field reverses 2.5 billion times in a second, the Mickey Mouse's head will rotate like a pinwheel. And in the process of turning around, the water molecules will rub against each other. This creates friction, which is the source of heat energy production.

A microwave can cook food faster than a conventional oven because it heats both inside and outside the food at the same time. An oven or frying pan at the beginning only heats the surface of the food, then the new heat progresses inside. But since only food is warming up, the air inside the microwave is still at room temperature, so the dish will not be as brown or crispy as when processed with other methods.