Microwave oven facts for kids

A microwave oven (often just called a microwave) is a kitchen appliance that cooks food using special microwaves. These microwaves are a type of radio wave. The idea for the microwave oven came about when a scientist was working with radio waves and noticed that a chocolate bar in his pocket had melted. This made him realize that radio waves could be used to heat food, leading to the invention of the microwave oven.

How Microwaves Cook Food

This is a magnetron from inside a microwave oven.

Microwave ovens use a special part called a magnetron. This magnetron works a bit like a radio transmitter. It creates very short radio waves. These waves go into your food, usually about 2.5 centimeters (one inch) deep.

When these waves hit the food, they make the water molecules inside it twist around incredibly fast. They twist about 2.5 billion times every second! This fast movement creates heat. As these water molecules get hot, they pass their heat to the molecules around them. This process is called conduction, which is how heat spreads through things.

In a regular oven, heat mostly stays near the surface of the food, so it takes longer to cook. But microwave energy goes deeper, which helps food cook much faster.

Inside the Microwave

Besides the magnetron, a microwave oven has a few other important parts. There's a wave guide, which directs the microwaves, and a turntable. There's also a timer switch.

When you put food inside and turn on the timer, the oven does two things:

• It tells the magnetron to start sending out microwaves.
• It tells the turntable to begin spinning.

The turntable spins the food around to make sure the microwaves heat it evenly. Microwaves are especially good at heating foods that contain "polar molecules," like water. These molecules are easily affected by the vibrating energy of the microwaves.

Why Metal Sparks in a Microwave

You should never put metal in a microwave oven. Metals tend to spark instead of heating up. This happens because metals easily give away their electrons. When microwaves "push" at these electrons, instead of just vibrating, the electrons are pushed off the metal. A lot of electrons moving off metal creates electricity, which you see as sparks.

Related pages

• Frozen dinner

Images for kids

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  A modern microwave oven (2022)

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  The cavity magnetron developed by John Randall and Harry Boot in 1940 at the University of Birmingham, England

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  Microwave ovens, several from the 1980s

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  Raytheon RadaRange aboard the NS Savannah nuclear-powered cargo ship, installed circa 1961

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  A microwave oven, c. 2005

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  A magnetron with section removed (magnet is not shown)

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  Inner space of a microwave oven and control panels.

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  In addition to their use in heating food, microwave ovens are widely used for heating in industrial processes. A microwave tunnel oven for softening plastic rods prior to extrusion.

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  Charred popcorn burnt by leaving the microwave oven on too long

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  A microwave oven with a metal shelf

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  A microwaved DVD-R disc showing the effects of electrical discharge through its metal film

See also

In Spanish: Horno de microondas para niños