Peggy Steiner, age 15, of Albuquerque, N.M., for her question:
HOW DOES A MICROWAVE OVEN WORK?
A microwave oven cooks food by using short radio waves that penetrate the food and make its molecules vibrate.
Friction among the moving molecules produces heat that cooks the food in a microwave oven. Microwaves pass through glass, paper and most kinds of china without heating them. Therefore, containers that are made of these materials may be used to hold food in a microwave oven.
A microwave oven has an electronic vacuum tube called a magnetron that produces microwaves. In most ovens, the microwaves move through a metal tube to the metal blades of a stirrer, a device similar to an electric fan. The moving blades of the stirrer scatter the microwaves into the oven. The waves bounce off the walls until they enter the food in the oven.
With most foods, microwave cooking generally takes much less cooking time than does gas or electric equipment. But the time needed depends on the amount of food that is being cooked. In a regular oven, for example, it takes 45 minutes to an hour to make one or several potatoes. In a microwave oven, it takes about three minutes to bake one potato, but it requires an extra two minutes of cooking time for each additional potato.
Electric ranges were first sold in 1909. Few people bought early models, since electric cooking was extremely slow.
A modern electric cooking unit was developed during the 1930s and at that time electric ranges became popular.
Microwave ovens were introduced in the mid 1950s and then they became extremely popular during the late 1970s.
Until the early 1800s, people in Canada and the United States used fireplaces for cooking and heating. By the 1830s, advances in ironmaking and transportation made cast iron widely available and iron stoves came along.
Early iron cookstoves burned wood. The first practical coal stove, called a baseburner, was patented in 1833 by an American inventor named Jordan Mott. Mott's stove was vented and it made coal burning efficient.
A German chemist named Robert Bunsen invented the first practical gas burner in 1855. In the 1860s, ranges based on Bunsen's burner became popular in cities that had gas piped into homes for use in gaslights.
Today cooking stoves are called ranges. A range has a cooktop with several heating areas and one or two ovens. Some ranges operate on gas while others use electricity.
Either natural gas or a liquefied petroleum gas can be used in gas ranges.
Many kitchens today add a microwave oven to the cooking range. This handy appliance helps to lighten cooking chores. Microwave ovens can be built in and used with either gas or electric ranges. Also, portable microwave units that stand next to ranges are extremely popular.