To put it very simply, a microwave
oven is a device in which food is cooked by the heat produced by
the absorption of microwave energy by water molecules in the food.
Microwave ovens operate by agitating the water molecules in the food,
causing them to vibrate, which produces heat. The microwaves enter
through openings in the top of the cooking cavity, where a stirrer
scatters them evenly throughout the oven. They are unable to enter a
metal container to heat food (causing sparks), but they can pass through
non-metal containers.
There are many microwave ovens available nowadays. All fall into three
main categories. The countertop microwaves are the most
popular and take up less space. Some have a rack or shelf, thus offering
two cooking positions and are more complicated to use. Usually the food
on the shelf gets more of the microwave energy than that on the base so
you have to select foods that will together satisfactorily. Remember,
timings will be different if cooking more than one item at a time. Double
oven microwaves are available as either freestanding cookers with
hob or as a double oven unit. (You can start cooking a joint of meat in
the microwave and then brown it in a conventional oven.)
Microwave ovens offer impressive speed and convenience. Today's
models have child lockouts with keypad releases. Other improvements
include automatic defrosting and a range of programmed power and time
settings for the most popular microwave foods, such as pizzas. Some
models even organize foods by ethnic category, such as Chinese and
Italian, and cook accordingly. These features apart, the real
differences are in power, capacity, cooking sensors, and convection-heat
options. Power is measured in watts, starting at 600 and ending near
1000. More power means shorter cooking times. Power is usually coupled
with size. With more power and you'll get a larger cabinet, plus a
carousel, which eliminates the need to stop and stir. Cabinet sizes
start at around 0.5 cubic feet and end near 1.3 cubic feet. Many models
have built-in sensors that prevent food from overcooking by monitoring
moisture levels. When a sensor determines that a meal has shed most of
its water through cooking, it signals that the meal is ready. Some
top-end models add convection heat so foods can be browned without
moving to a conventional oven before serving

