Microwave oven facts for kids
A modern microwave oven (2022)
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| Type | Appliance |
|---|---|
| Inventor | Percy Spencer |
| Inception | 1947 |
| Manufacturer | Various |
| Available | Globally |
| Website | Lua error in Module:WikidataIB at line 168: attempt to index field 'wikibase' (a nil value). |
A microwave oven, often just called a microwave, is a kitchen appliance that cooks and heats food very quickly. It uses special invisible energy waves called microwaves. These waves cause the water molecules inside food to vibrate at a very high speed. This vibration creates heat, which cooks the food. Microwaves are great for reheating leftovers, defrosting frozen food, and making popcorn in just a few minutes.
Contents
How a Microwave Works
A microwave oven uses a special device called a magnetron to create microwaves. When you press the start button, the magnetron converts electricity into these high-powered energy waves. The waves are then guided into the main cooking compartment.
The inside of a microwave is a metal box that acts like a room full of mirrors for the microwaves. The waves bounce off the metal walls and hit the food from every direction. Most microwaves also have a spinning glass plate, called a turntable, to make sure the food cooks evenly.
Microwaves can pass through materials like glass, paper, and most plastics. However, they are absorbed by the water, fats, and sugars in food. When the microwaves hit the food, they make the tiny water molecules inside it spin around millions of times per second. This rapid spinning creates friction, which produces heat and cooks the food.
It's a common myth that microwaves cook food from the "inside out." They actually cook the outer layers first, just like a regular oven. The heat then travels toward the center of the food. Because this process happens so fast, it can sometimes seem like the food is cooking from the inside.
A Sweet Accidental Invention
The microwave oven was invented by accident after World War II. The technology behind it, however, was created during the war.
The Cavity Magnetron
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During World War II, two British scientists, John Randall and Harry Boot, invented the cavity magnetron. This device could produce powerful microwaves. It was a key part of radar systems, which were used to spot enemy ships and planes from far away. The magnetron was a top-secret invention that helped the Allies during the war.
A Melted Candy Bar
After the war, an American engineer named Percy Spencer was working at the company Raytheon. He was testing a new magnetron for a radar set. During his work, he noticed something strange: a candy bar in his pocket had completely melted.
Spencer was curious and realized the microwaves from the magnetron must have heated the candy. To test his idea, he placed some popcorn kernels near the device. A few moments later, they started popping all over the lab! His next experiment was with an egg, which cooked so fast that it exploded. Spencer had discovered a whole new way to cook food.
The First Microwaves
In 1947, Raytheon built the first commercial microwave oven, called the "Radarange." It was not something you could put on your kitchen counter. It was almost 6 feet tall, weighed over 750 pounds (340 kg), and cost about $5,000. These giant ovens were water-cooled and were only used in places like restaurants and on ships.
Microwaves Come Home
Over the next 20 years, companies worked to make microwave ovens smaller, safer, and cheaper. In 1967, the first countertop microwave oven for home use was introduced. It was still expensive, but it was a big step forward.
By the late 1970s and 1980s, the price of microwave ovens dropped quickly. They became very popular, and soon, almost every home had one. Today, over 90% of households in countries like the United States have a microwave oven in their kitchen.
Microwave Safety Rules
Microwave ovens are very safe when used correctly. The oven has safety features that stop the microwaves as soon as you open the door. Here are some important rules to follow.
Metal in the Microwave
You should never put metal objects in a microwave oven. This includes forks, spoons, steel wool, and most types of aluminum foil. Metal reflects microwaves, which can cause sparks, a fire, or damage to the oven.
The sparks happen because the microwaves create an electric charge in the metal, especially on sharp edges like the tines of a fork. This can create a small lightning bolt inside your microwave!
Some microwave ovens come with metal racks. These are specially designed to be safe, but you should always follow the manufacturer's instructions.
Safe Containers
Always use dishes and containers that are labeled "microwave-safe."
- Good choices: Glass and ceramic dishes are usually safe for the microwave.
- Be careful with plastic: Some plastic containers can melt or release chemicals into your food when heated. Only use plastics that have the microwave-safe symbol (often three wavy lines).
- Never use: Metal pans, single-use plastic containers (like yogurt cups), or foam containers.
Other Safety Tips
- Don't heat sealed containers. Heating food in a container with a tight lid, like a jar, can be dangerous. Steam builds up inside and can cause it to explode. The same thing can happen if you try to cook an egg in its shell.
- Be careful with liquids. Sometimes, water can be heated in a microwave past its boiling point without actually bubbling. This is called superheating. If the water is then bumped, it can suddenly erupt out of the cup and cause a serious burn. To be safe, stir liquids before and after heating them.
- Never run an empty microwave. If there is no food inside to absorb the energy, the microwaves can bounce back and damage the oven.
- Watch your cooking time. Food can go from cooked to burnt very quickly in a microwave. Always follow the recommended cooking times and keep an eye on your food.
How to Use Your Microwave: a step-by-step guide
- Use glass, ceramic, or plastic containers clearly labeled "Microwave-Safe."
- Place the container in the center of the glass turntable. This ensures even cooking.
- Ensure the door is firmly closed. The microwave will not operate if the door is ajar.
- Set the Power Level
Most people only use "High" (100% power), but adjusting the power is key to heating food evenly without burning it.
High (100%): Best for boiling water, cooking vegetables, and reheating beverages.
Medium-High (70-80%): Good for reheating dense foods like mashed potatoes, casseroles, or meat. It heats them through without making the edges rubbery.
Medium (50%): Perfect for melting chocolate or butter gently, or for defrosting delicate foods.
Low (30%): Ideal for keeping food warm or slowly defrosting larger items.
How to adjust it: Look for a button labeled "Power," "Level," or "Cook." Press it, then enter the power percentage or use the number pad (e.g., press "5" for 50% power). Then enter the time.
- Use the number pad to enter the desired time (e.g., 1:30 for one minute and thirty seconds).
- If your microwave has quick-start buttons (like "Add 30 Sec"), you can use those for convenience.
- Press the "Start" button.
- Listen for the sound. The hum is normal. If you hear loud popping or sparking, stop the microwave immediately and check for metal.
- The container and food will be HOT! Always use oven mitts or a dry towel to remove it.
- Be cautious of steam when removing lids or plastic wrap; lift the far side away from you.
Quick Cheat Sheet for Reheating
- Soups & Sauces: Cover with a lid or paper towel to prevent splatters. Heat on High for 2-3 minutes, stir, then continue in 1-minute increments.
- Leftovers (Pizza, Casserole, Pasta): Place on a microwave-safe plate. Sprinkle a few drops of water on it and cover with a damp paper towel. This adds steam and prevents drying out. Heat on Medium (50%) for 1-2 minutes.
- Rice & Grains: Add a tablespoon of water per cup of rice before reheating. Cover and heat on Medium-High.
- Bread & Baked Goods: Heat on Low (30%) for short bursts (15-20 seconds) to avoid making them tough and chewy.
Related pages
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
