How the Oven Works
The microwave works when the high voltage is converted to waves of electromagnetic energy, which is a combination of electrical and magnetic energy. This energy is in the frequency band of radio waves, not x-rays. A wave guide and stirrer blade work together to make sure the energy reaches all areas of the oven interior. When the door is opened or the timer reaches zero, the energy automatically stops, so no microwave radiation leaves the oven. All ovens also have two independent systems that ensure the electrical activity stops as soon as the door is opened.
The microwaves make the water molecules contained in food vibrate and 'wiggle', which produces heat. This is what cooks the food, and also why the oven itself doesn't heat up. That's why foods that have a lot of water, like fruits and vegetables, cook more quickly. Foods high in fat and sugar also cook more quickly. Metal reflects the microwaves, and the energy passes through glass, plastic and paper. As soon as the microwave energy is absorbed by the food, it is converted to heat - so the microwave energy can't 'contaminate' the food.
Although heat is produced directly in the food, microwave energy doesn't cook food from the inside out. More dense foods like meat are cooked primarily by conduction of heat from the outer layers, which are heated by microwaves.
In combination microwave/convention ovens, you'll notice that the interior is metal. A convection oven's special feature is a fan that constantly circulates hot air around the food, so it cooks more quickly and browns very evenly. Follow the cooking instructions to the letter if you have one of these appliances.
Never try to repair your own microwave. It is a complex appliance that includes a magnetron, high voltage transformer, thermal protectors, and complicated circuits.
Go to the next page to learn about microwave safety.