How do Microwave Ovens Work – Summary of Key Points

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A question came up from the community again and it was how does a Microwave oven work so if you would like to know the key points summarized, then take a quick look through this post.

Microwave ovens are wonderful appliances and a boon for those persons who do not want to cook much and only need to reheat food quickly and efficiently.  Microwave ovens are quick and efficient because they directly heat the food instead of the oven or the container of the food.

The molecules of the food absorb the microwave radiation energy directly convert it to heat energy thereby increasing the temperature of the food. Water, fats, and sugar most readily absorb the microwaves, so foods which contain more water, fats or sugar more readily cooked in the microwave oven.

Microwave Overview

Microwaves are electromagnetic radiation just like the radio waves, x-rays.   They can carry a lot of energy. The frequency of microwaves used in current household microwave ovens is 2.45 GHz.

Microwave Oven Components

The Oven Box

It is a metallic box which is so made that microwaves cannot escape it. On the front side is the door. It has a glass window so that you can see inside while the food is being cooked. The glass window has a metallic mesh embedded in it to ensure that microwaves do not leak through the glass window. There is a rotating glass plate which slowly spins by an electric motor. Food is placed on the rotating glass plate.

This helps in absorption of microwaves by the food more uniformly and thereby the food gets cooked evenly. There is an interlocking mechanism that shuts off the microwave oven if the door is opened.

Transformer and other Electronic Components

There is a heavy transformer to convert the 110 volts household current to 3000 volts or more. This high voltage is required by the magnetron. There are various other components such as capacitors, resistors and other power electronics components.

Magnetron

This is the key component of the microwave oven. It is a vacuum tube which generates the microwaves of the required frequency and power. Inside the magnetron voltage is applied to a filament which is heated and it releases electrons due to thermionic emission. These electrons are accelerated by the electric field. A magnetic field is applied to these electrons by two ring magnets. The electrons move in a circular motion and it creates an oscillating electric and magnetic field due to the moving charge. A resonance occurs and this generates microwaves. A cooling fan cools the magnetron.

Waveguide/Antenna

An antenna is connected with the magnetron to propagate the microwaves generated by it, into the microwave oven box. It is also called the waveguide.

Control Panel

On the front, just beside the door, there are a few dials and push buttons which allow you to set power levels at which you want the food to be cooked. There is also timer mechanism by which you can set the time of the cooking, after which the microwave oven would shut itself off. On newer models, the control panel consists of touch buttons.

Operation of a Microwave Oven

1. Open the microwave door and place your food in a container on the turntable.

2. Close the door and set power level and time to cook.

3. Push the start button.

4. The turntable starts to spin slowly with food on top of it.

5. AC current flows into the transformer and it fires up the magnetron within 2 seconds.

6. Microwaves are produced in the magnetron and are propagated into the microwave oven box via the antenna and waveguide.

7. The microwaves get reflected by the wall the oven box until they are absorbed by the food.

8. The water molecules in the food absorb the microwave energy, get excited, oscillate and generate heat with raises the temperature of the food. This cooks the food.

9. When the timer runs out, the microwave shuts itself off.

10. Now you can take the food out safely.

Final Points to Note...

A microwave oven can only heat water molecules in the food and to some extent fats and sugars. However, anything dry, glass and most plastics do not absorb microwaves are not heated by the microwaves. Dry food cannot be cooked in a microwave oven. Containers used in microwave ovens should only be made of heat resistant glass or ‘microwave safe’ plastics. No metal containers or anything containing metal should be used.

 

While you are here, feel free to view larger or the stock levels of a selection of popular Microwave Ovens by clicking on any of the images provided below…

 

Finally, it would be greatly appreciated by the community if you can share your own experiences of using a Microwave Oven good or bad by leaving a comment in the comment box below – So that people in the community can learn also!

 

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