MadSci Network: Engineering

Re: More details about how a microwave works?

Date: Sat Jul 15 11:04:14 2000
Posted By: Edward Peterson, Staff, Chemical Engineering, S&B Engineers and Constructors
Area of science: Engineering
ID: 963245781.Eg

Dear Emily,

Your question is very open ended, so I don't know how much detail to 
provide or even if I can answer your question.

I will assume that you want to know how a microwave "Oven" works.  A 
microwave by itself is a form of electromagnetic energy that has a 
frequeny in the range of 300 megahertz to about 100 Gigahertz.  This is 
not a fixed range and various people accepth different ranges.

A microwave oven is one way to expose matter to microwave energy.  The 
interaction of microwave energy with matter results in the conversion of 
this form of electromagnetic energy into heat.  The heat is created when 
microwave energy interacts with molecular dipoles, twisting them and 
making them move back and forth.  Dipoles exist in matter when a molecule 
is composed of different chemicals, such as carbon and oxygen, and there 
are chemical bonds that these atoms share.  When one holds electrons more 
strongly than the other, the bond is polarized, having a more negative end 
and a more positive end.  The microwave, being electromagnetic energy, is 
composed of electrical and magnetic fields.  If the dipole is an 
electrical dipole, as most chemical dipoles are, the microwave electrical 
field in a microwave oven changes direction 5.9 billion times a second.  
Each field reversal tugs at the dipole a little bit, causing the dipole to 
twist and turn the molecule that it is attached to a little.  That little 
tug and twist multiplied by about 6 billion each second results in a lot 
of heat.

That is a little knowledge.  If you need to know more, or you have a more 
specific question, you can write me directly at

Dr. Ed Peterson

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