A combination of electrical and mechanical devices control the microwave energy used for heating and cooking foods in a microwave oven. Electricity from the power cord enters the oven through a series of circuits and fuses. The energy reaches the food from every direction due to the design of the microwave.
A microwave oven cooks food with radio waves. The frequency used in many ovens is 25,000 Mhz. These waves are absorbed by the water, fat and sugar in food. The waves are converted to energy or heat, which reacts with most plastic, glass or ceramic. Metal reflects this heat, and that is why you cannot use metal pans in a microwave oven.
The Cooking Process
In a microwave oven, the radio waves heat or penetrate the food almost immediately through the water and fat molecules. The heat spreads through the food evenly right away. It does not heat from the outside to the center as in a conventional oven. However, radio waves penetrate unevenly in some thick pieces of food.
A microwave heats by exciting atoms in the food not conducting heat. The temperature in the microwave oven is at room temperature. It is hard to brown a crust on pies and breads in a microwave. Sometimes it is hard to heat some foods consistently because of the way it works.
A microwave is great to heat, defrost and cook some foods. Because radio waves are not absorbed the same in all foods, cold spots can occur. Ways to eliminate cold spots is to rotate food once or twice when cooking or stirring in a covered dish in the microwave. When defrosting food in a microwave, remove any foil or plastic wrap as it may melt or burn. If you defrost meat, cook it immediately in the stove to avoid food contamination. The microwave is great for reheating leftover food and reheating coffee. It is a convenience item that reduces time for cooking and heating food.