microwav

	In a microwave oven a magnetron generates microwaves, which are really just high frequency radio waves. The microwaves make some kinds of molecules, like the water molecules in food, vibrate very rapidly. In most ovens they vibrate back and forth 2,450 million times per second. In doing so the molecules get hot and heat the food. Plastic and china do not contain the right kinds of molecules so they stay cool except where they are in contact with the hot food. A magnetron consists of a cylindrical cathode inside a cylindrical copper anode with an even number of vanes pointing in towards the centre.Alternate vanes are connected with strap rings and the interior is pumped to a vacuum. An antenna joined to one of the vanes conducts the microwaves outside.
	When the cathode is heated by an electric current electrons are given off. The negatively charged electrons are attracted to the positively charged anode as a negative potential of 4000 volts is applied to the cathode. Normally the electrons would travel in a straight line as shown in the diagram. However...........
	A strong magnetic field is provided by magnets placed on either side of the anode. As a result...............

	.........the magnetic field causes the electrons to take an orbital path as shown in the diagram
	As the orbiting electrons pass close to anode vanes that are alternatively connected the electron cloud takes on a rotating 'paddle wheel' shape. As the 'paddles' travel past the cavities between each of the anode vanes they produce a pulse of electromagnetic radiation in the cavity. The energy is radiated from the magnetron by the antenna (see diagram at the top of this page) and conducted to the oven through a hollow tube.
Microwave Oven Safety	When switched off light globes do not continue to produce light, likewise magnetrons can't produce electromagnetic radiation when they are turned off. Microwave ovens are carefully designed to prevent the electromagnetic radiation inside the operating oven from escaping. Never operate the oven with the cabinet removed. Keep the oven interior and the door seal clean. If there is any sign of corrosion around the door or the door doesn't shut properly don't use the oven until it is tested by a certified tester. Metal reflects microwaves and may disturb the distribution in the oven so that some of the food may not cook properly or it may reflect microwaves back to the magnetron, damaging it. Small pieces of metal or gold edges on plates can act as an antenna and build up a high voltage. This may cause arcing or sparking and may burn through the paint on the oven walls.