Microwave ovens, now common to most U.S. households, use advanced technology to simplify cooking. Unlike traditional cooking appliances, microwave ovens have no heating elements. Inside the microwave oven, your food is bombarded by electromagnetic radiation. Food molecules become physically agitated due to exposure of EM energy. Heat generated inside the food, not the oven, cooks your food.
Shell or Case
The shell or case of the microwave oven, including the inner cooking chamber, is typically made of a steel alloy. Since microwave radiation is reflected by steel, the case prevents radiation from escaping when the oven is turned on. The viewing panel in the oven door is typically made of glass and a metal mesh that also prevents microwaves from leaking out of the oven. The electronic circuits, transformer and magnetron are housed between the inner and outer walls of the oven.
Depending on the oven's features, the microwave's operating console may be only a mechanical timer switch. Some ovens that have more advanced features may be operated by space-saving electronic control panels. Special features of higher-end models may include an intermittent timer for thawing and slow cooking, a clock or kitchen timer, a delay timer, browning or convection capabilities.
To create microwave radiation, the magnetron must be supplied with a high-voltage current, between 3,000 to 5,000 volts. Household current in the U.S. is supplied at only 120 volts. The transformer, made of copper wire wrapped around an iron core, takes incoming current from a standard 120 volt electrical socket and uses electromagnetic induction to increase its voltage up to 40 times its original value.
The magnetron is a specialised vacuum diode tube that transforms electrical current into EM energy in the form of microwaves. The magnetron's essential components are an anode (positively charged diode), an electron-emitting cathode (negatively-charged diode) and a magnet. Used in conjunction with a capacitor, the magnetron produces microwave radiation with frequencies and wavelengths sufficient to interact with water-containing food at the molecular level.