While there are many different styles of microwaves, several primary devices remain the same throughout different models. Microwaves have become very automated and the addition of sensors have made them much more effective and safe to use, but the original design still holds true.
A microwave oven is made of two separate and interworking parts: the control section and the high-voltage section. The control section channels the electricity from the house grid to the microwave itself in a safe manner. The high-voltage section then does most of the work, taking the electricity and changing it into microwave rays that are then emitted into the cooking chamber. Both sections have security devices to ensure that microwaves do not dangerously malfunction or operate incorrectly.
The triac is a device in the control section that helps channel electricity. This electromechanical relay normally seals the circuits of the microwave away from the electricity flowing through the outlet. When the microwave is turned on, sensors indicate that all the devices are working and ready to produce the microwaves themselves. The triac then switches into an "on" position, allowing the electrical current to flow to the high voltage transformer.
High Voltage Transformer
The microwave takes more power to work than the normal voltage of the household current produces. Fortunately, a device called the high voltage transformer takes care of this problem. Essentially, the high voltage transformer is a series of capacitors that spreads and loops the current to make it much more powerful, usually around 3000 volts from the normal 115 of American household electricity.
With the voltage high enough, the current is then passed on to the magnetron tube, which turns the current into microwave energy. This specially made diode uses magnetic fields to control electrons so that as they pass through the diode they heat up the filament/cathode, which causes many of the electrons to split off in the form of microwave energy.
Once the microwave energy is created, it is channeled into the cooking chamber by the wave guide. There is usually another device that helps scatter or spread the microwaves so they fill the chamber effectively; sometimes a stirrer blade is used to "stir" the microwaves so they spread out or the tray on which the food is placed rotates itself.
The microwave energy produced by microwave ovens can be very dangerous to humans, which is why the cooking chamber is carefully protected by a sealed frame that keeps any microwaves from escaping. The door to microwaves is covered by a thin metal grid with spaced holes that are too small for any microwaves to pass through, but allow the user to see into the chamber.