How a microwave works?

By Tyler Miller

The Microwave Oven

• The first personal microwave was introduced in 1967 by the Amana Corporation. The first microwave for home use was introduced by Tappan in 1955.

• The heating effect of microwaves was discovered accidentally in 1945.

The Microwave Oven

• Percy Spencer, an American self-taught engineer from Howland, Maine, was building magnetrons for radar sets with the American company Raytheon. He was working on an active radar set when he noticed that a peanut chocolate bar he had in his pocket started to melt. The radar had melted his chocolate bar with microwaves.

How do they work?

• There's a transmitter inside the microwave that sets up an electromagnetic field when you press "start" and radiates microwaves at a certain frequency just within the confines of the microwave. These microwaves are special in that they are readily absorbed by water and a few other organic materials, but less so by materials like plastic and glass.

How do they work?

• This means that when the microwaves hits the food, most of the organic molecules inside the food start to jiggle, creating heat. This causes the food to warm up quickly and relatively evenly while the container itself stays cool. The material of some containers will still absorb microwaves and will get hot if microwaved for long periods of time.

How do they work?

• A high voltage power source, commonly a simple transformer or an electronic power converter, which passes energy to the magnetron

• A high voltage capacitor connected to the magnetron, transformer and via a diode to the case.

• A cavity magnetron, which converts high-voltage electric energy to microwave radiation.

• A magnetron control circuit

Why don’t microwaves escape from the microwave oven?

• You may be wondering how microwaves are reflected by the door on a microwave oven, if they are able to pass tens of miles from mobile phone transmitters through solid walls and into our mobile phones?

• The door of a microwave oven is designed to reflect microwaves so that they can't escape from the oven. That mesh in the door isn't plastic, it's metal. Metal surfaces reflect microwaves and, even though the mesh has holes in it to allow you to observe the food, it acts as a mirror for the microwaves.

Why don’t microwaves escape from the microwave oven?

• Microwaves have a wavelength of 12.2cm so they can not pass through the 2mm metal holes.