February 19

How Does a Microwave Oven Work? – 7 Components Explained


Author: Ana Stanar
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For an invention that came about as an accident, the microwave is undoubtedly a vital household appliance.

In just a matter of seconds, a cold meal can be piping hot, saving the user a lot of time as well as effort since all this can be controlled by the press of a few buttons or even the turn of a knob.

The first commercially available microwave was made available in 1947, just a few years after the Second World War.

Modern microwaves are much smaller than their predecessors, some of which stood at over 5-feet tall and weighed hundreds of pounds.

Over the decades, the working principle has remained relatively the same.

In this article, we will look at how does a microwave oven work in the simplest words possible. We also reviewed Toshiba EM131A5C-SS  and you can also take a look at our Panasonic NN-sn766s review when you’re done reading this post.

What are Microwaves?

How Does a Microwave Oven Work
The image shows the frequency and wavelength of microwaves in the larger electromagnetic spectrum. Source: Wisegeek

Several kinds of electromagnetic radiation exist. Radio waves, X-rays and Gamma rays are some examples and microwaves also belong in the same group.

These waves are essential for many day to day tasks and have been used in radar systems and also have applications in communications such as mobile phones.

Many people are also familiar with the use of this radiation for cooking in a microwave oven.

The typical frequency range for microwaves is between 1 and 300 Gigahertz with a wavelength ranging between 1 millimeter and 30 centimeters.

Microwave Oven Components

How Does a Microwave Oven Work

To understand how a microwave oven works, we need to gain some understanding of the various components of the device.

This will show what each component does, therefore, paint a picture of how the whole device works with all the systems tied together.

1. The Magnetron Assembly

Magentron Assembly
Magentron Assembly is the critical component of generating microwave energy

This is the component that generates the microwave energy which is in turn used to heat the food.

The magnetron generates these waves using very high voltages. The typical electric voltage from a household wall socket is usually quite low to fulfill this need. Therefore a transformer is used. (discussed below)

At the center of the magnetron assembly is a filament that gets heated therefore releasing streams of electrons.

The assembly is also composed of a pair of ring magnets which deflect the electrons back to the cathode so that they don’t fly directly to the anode. As a result, the electrons move in a circular path within the assembly.

The anode is made up of cavities and as the electrons go through these at very high speeds, microwaves are created.

Older magnetrons were very large and quite fragile compared to new ones. Their typical size meant that the devices themselves needed to be generally larger as well. However, with the development of new materials and better ceramics, the assembly became smaller, allowing for small profile microwaves.

Also Read: Where to recycle my microwave?

2. The Waveguide

The Waveguide Cover.

Connected to the microwave’s magnetron is a waveguide. What is a waveguide? It is a hollow metallic tube that helps to transmit microwaves along a certain path by making use of successive reflections within the surface of its inner walls.

A microwave oven would typically use this to transmit the waves produced by the magnetron to the internal cavity where the food is placed.

They are easy to manufacture and offer a lot of benefits including shielding as they have very minimal energy losses.

Once this component gets damaged, you should consider replacing it as soon as possible before resuming your use of the appliance to avoid any personal injuries.

3. The Transformer

The Transformer
The Transformer

Transformers are fairly simple electrical devices that are essential for most electronic devices. They are used to convert AC (Alternating Current) voltages from one voltage level to another.

As mentioned, microwave ovens are high power devices. They need high voltages to work sufficiently and the typical household’s wall outlet voltage just isn’t enough.

A step-up transformer is used to transform this relatively low voltage to a high enough value for use within a microwave oven.

The device needs about 4000 volts or more to generate the microwaves and it’s the job of the transformer to supply this voltage to the magnetron assembly which will, in turn, produce the waves when it is operational.

4. Cooling Fan

As heating occurs in the microwave, it is necessary to have a system in place that ensures the components do not overheat.

For that reason, some microwave ovens come with a cooling fan.

This is used to dissipate the heat generated by the microwave’s components as do most electronics do.

Older models also made use of a stirrer fan at the top of the cavity that was used to circulate the microwaves within the cavity for more even cooking.

5. The Control Panel

This is the main component that users interact with.

From here, you can set the duration, the level of intensity with which you want to cook the food, and even the operation you want to do, whether it is grilling, defrosting or microwaving a meal.

The control panel lets you control the device how intuitive the interface is will depend on the device’s manufacturer and the model.

6. The Door

Most microwaves will have a glass door that lets you see the food inside. This lets you monitor your food allowing you to choose to interrupt any process if need be.

Another function of the door is to keep the microwaves inside the cavity of the device where the food is.

Microwaves can cause burns when they leak out of the device and to counter this, the door is fitted with a metal mesh whose holes allow you to see through but aren’t large enough to allow waves to escape.

Also, the door lets you put your food inside the device.

7. The Case

This makes up the body of the device. The case’s purpose is to protect the microwave’s components from damage and the elements like dust and excessive moisture.

Additionally, it helps protect the user from harmful escaping microwaves during operation.

Also Read: How to remove yellow stains from microwave?

The Microwave’s Working Principle

Microwave Oven Vibrates
Microwave oven vibrates molecules inside the food. Image Source: Scientific American

When you initiate a task, current enters the magnetron assembly and heats a filament inside it. This acts as a cathode and once heated, it releases electrons.

These are accumulated and used to generate the microwaves which are then guided to the cavity where the food is placed.

The waves themselves do not carry thermal energy. Unlike in non-microwave ovens where a heating element is used, microwave ovens cook food by generating the heat from within the food itself.

This happens due to vibrations.

The waves are absorbed by certain molecules within the food which in turn causes them to vibrate. This vibration produces kinetic energy which is then converted to heat energy and the food gets heated or cooked.

Also Read: How to reheat french fries in Microwave?

It’s All Connected!

Every single part of the microwave is essential for it to perform at its best.

The various components work together as a singular entity to perform the desired function. The onboard computer that a user interacts with via the control panel sets the pace for the tasks that the rest of the components will do.

This can help control the amount of power going into the device and when to switch the magnetron on and off depending on what the user has set.

Likewise, components such as the turntable turn the food around for better and more even heating which is further improved by having inner walls made of metal which reflects the wave through the food.

The hum you hear when the microwave is running is the transformer, and some other components working to step up the low voltage received from the power supply to a higher level that can be utilized by the magnetron.

You may also hear the fan running, driving cool air through the magnetron assembly to cool it down.

You may notice that if you open the microwave oven’s door while it’s running, it instantly turns off.

This is a safety mechanism that is built into the ovens to prevent accidental escape of the harmful microwaves.

Using a Microwave Oven

Most microwave ovens are very straightforward to use. However, be sure to consult the user’s manual that accompanies the device if you’re unsure.

The basic use case involves selecting the function you want from the control panel. You can heat, grill, bake or defrost food on many models.

You will also need to choose the amount of time it should take.

Some models allow you to select the power level for when you’re warming food just for extra control of what happens inside.


This small guide aimed to helped you understand how does a microwave oven work in the most simplest words possible.

Whether you are an engineer or a chef trying to understand your cooking devices, the technical knowledge can come in handy.

Just a few decades after their invention, microwaves have proven to be invaluable assets in the household.

They have improved efficiency in the kitchen by reducing the time and effort needed to perform some cooking tasks.

Microwave ovens function differently from conventional ovens in that they induce the heating from within the food itself rather than transmitting the heat from an external heating element.

This makes cooking with a microwave much faster and in some cases, more efficient as well.

The device itself is made up of many subsystems which when combined, work together to serve a purpose that had taken our ancestors a lot of time and effort. Cooking a meal.


1. How does a microwave oven work physics?

By bouncing electrons around inside a vacuum-filled cavity exposed to a strong magnetic field, the magnetron generates microwave radiation. These electrons are compelled to circle around inside the cavity by the magnetic field, absorbing energy. This energy is eventually released in the form of a microwave.

2. How does a microwave oven use microwaves to quickly heat food?

Microwaves, like radio waves, can pass directly through the walls of your home. Because vibrating molecules generate heat, the more rapidly they vibrate, the hotter the food becomes. Thus, microwaves transfer their energy to the food's molecules, rapidly heating it.

3. Why can't you put metal in a microwave?

Metals, such as forks, knives, and spoons, are excellent conductors of electricity due to their abundance of free-moving electrons. Microwaves are reflected when they come into contact with metal objects, which can cause problems. As a general rule, avoid placing metal objects in microwave ovens.

4. Why do most microwave ovens have turntables?

Turntables in microwaves rotate the food to ensure even cooking. This is because microwaves cook food from the inside out, so if something is not rotating, then one side will be overcooked and the other side will be undercooked.

5. How long should a microwave last?

Approximately seven years.

With normal use, the average microwave oven lasts approximately seven years, and even less with heavy use and poor maintenance. A large family may find that they need to replace their appliance every four to five years as they become more reliant on it to heat snacks and leftovers and defrost meals.

About the author

Ana Stanar

An Art Teacher, entrepreneur, and a mother of three, Ana considers cooking a form of art - pleasure for all senses as well as a process that requires creativity, passion and devotion. Since she leads a busy life, Ana just loves testing various kitchen appliances for Kitchen Gearoid, especially those that save her time while preparing food and cooking but also make every meal a masterpiece!


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