Science of the Microwave

Patrick de la LlanaDate: 10/15/12

History/Recap• Discovered in WW2 by allies for transmitting

information.• Waves transmit information by sending out

certain frequency, which radio transmitter picks up.

• Radio transmitter changes human voice into waves by varying frequency of radio waves in the same pattern as sound waves measured by the microphone.

• This process is known as Frequency Modulation (FM).

History/Recap

• Varying amplitude of wave is called Amplitude Modulation (AM).

• Difference in frequency defines what kind of wave it is.

Waves

Waves

Microwave Oven

• First made by Percy Spencer who was a self taught engineer.

• Worked for Raytheon, and discovered use for heating food by working in lab.

• Works by passing non-ionizing microwave radiation.

• In Electromagnetic spectrum lie between radio and infrared frequencies.

Microwave Oven

• Food, water and other things to eat absorb microwaves and heat up by dielectric heating.

• Dielectric heating=When radiation heats up a dielectric material. Temperature is raiesd by subjecting material to high frequency electromagnetic field.– Vibrates polarized molecules which heat up food.– Radiation causes dielectric heating.

Parts of Microwave

• Control Panel=Allows electric current to flow to transformer.

• Transformer and Capacitor=supercharge electricity, and feed electricity to magnetron– Transformer=changes current and/or voltage into

desired level.– Capacitor=Stores electricity, but in this case

soothes current.

Pictures

• Control panel• Inner parts of a Microwave

Magnetron• Empty tube with magnets around it. The copper

wire receives electric current from transformer and capacitor. Magnets create magnetic field which make electricity flow out of wire in beams of electrons.

• Each time electrons hit edge of wall, they return back in a circulation motion. This results in microwaves– Antenna inside magnetron send out microwaves to

waveguide– Basically converts electrical energy to radiation.

Magnetron

Parts of Microwave

• Waveguide=Guides microwaves into cooking chamber. Does this by confining the space of the releasing microwaves from the magnetron

• Cooking chamber=Chamber that confines the output radiation so that food can get heated up.

Another look at a microwave

Sources

•http://www.ccmr.cornell.edu/education/ask/index.html?quid=776•http://en.wikipedia.org/wiki/Microwave_oven•http://en.wikipedia.org/wiki/Dielectric_heating•http://ffden-2.phys.uaf.edu/212_spring2005.web.dir/Danielle_Ryder/The%20Physics%20of%20the%20Microwave%20Oven-%20Home.html•http://en.wikipedia.org/wiki/Dielectric•http://www.britannica.com/EBchecked/topic/162649/dielectric-heating•http://science.discovery.com/tv-shows/deconstructed/videos/deconstructed-how-microwave-ovens-work.htm•http://www.nrao.edu/index.php/learn/radioastronomy/radiowaves•http://www.radio-electronics.com/info/antennas/waveguide/waveguide-basics-tutorial.php