Description of function
19
How the microwave oven
works
In a microwave oven there is a high-
frequency tube called a magnetron.
This converts electrical energy into
microwaves. These microwaves are
distributed evenly throughout the oven
interior, and are reflected off the metal
appliance walls. This enables the
microwaves to reach the food from all
sides and heat it up. Microwave
distribution is improved with the
turntable engaged.
In order for microwaves to reach the
food, they must be able to penetrate the
cooking container being used.
Microwaves can pass through
porcelain, glass, cardboard and
plastics, but not metal. Do not,
therefore, use utensils made of metal,
or which contain metal, for example in
the form of gold or silver trim. The metal
reflects microwaves and this could
cause sparking. The microwaves
cannot be absorbed.
Microwaves pass through a suitable
container and find their way directly into
the food. All food contains moisture
molecules which, when subjected to
microwave energy, start to oscillate 2.5
thousand million times a second. The
friction caused by this vibration creates
heat. It first starts developing around
the outside of the food and then slowly
penetrates towards the centre. The
moisture content of food will affect the
speed at which it is cooked.
As heat is produced directly in the food,
this has the following advantages:
– Food can generally be cooked without
adding liquid or cooking oil, or with just
a little water or oil.
– Cooking, reheating and defrosting in a
microwave oven is quicker than using
conventional methods.
– Nutrients, such as vitamins and
minerals, are generally retained.
– The colour, texture and taste of food
are not impaired.
Microwaves stop being produced as
soon as the cooking process is
interrupted or the appliance door is
opened. When the appliance is in
operation, the closed, sealed door
prevents microwaves escaping from the
appliance.