Microwave Ovens
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
seminar surveyer
Active In SP

Posts: 3,541
Joined: Sep 2010
19-01-2011, 03:05 PM


If you put a CD in a microwave oven, it will

do nothing.
burn up the microwave oven.
burn up the CD.

Observations About Microwaves

Microwave ovens cook food from inside out
They can cook foods unevenly
They don’t defrost foods well
You shouldn’t put metal inside them?!
Do they make food radioactive or toxic?

Electromagnetic Spectrum

Long-wavelength EM waves: Radio & Microwave
Medium-wavelength: IR, Visible, UV light
Short-wavelength: X-rays & Gamma-rays

Water Molecules

Water molecules are unusually polar
An electric field orients water molecules
A fluctuating electric field causes water
molecules to fluctuate in orientation

Microwave Heating

Microwaves have fluctuating electric fields
Water molecules orient back and forth
Liquid water heats due to molecular “friction”
Ice doesn’t heat due to orientational stiffness
Steam doesn’t heat due to lack of “friction”
Food’s liquid water content heats the food

Effects of Microwaves

Non-Conductors: Polarization
Mobile, polar molecules orient and heat
Immobile, polar molecules do nothing much
Non-polar molecules do nothing much
Conductors: Current flow
Good, thick conductors reflect microwaves
Poor conductors experience resistive heating
Thin conductors experience resistive heating


Identical waves that overlap can interfere
Interference is when the fields add or cancel
Adding fields are constructive interference
Canceling fields are destructive interference
Reflects cause interference in a microwave
Interference causes uneven cooking
Good microwaves “stir” waves or move food

Generating Microwaves

Magnetron tube has tank circuits in it
Streams of electrons amplify tank oscillations
A loop of wire extracts energy from tanks
A short ¼-wave antenna emits the microwaves

For more

smart paper boy
Active In SP

Posts: 2,053
Joined: Jun 2011
12-08-2011, 04:35 PM

.ppt   MicrowaveOven.ppt (Size: 858.5 KB / Downloads: 97)
How a Microwave Oven Works?
What are Microwaves?

Microwaves are a form of electromagnetic energy, like light waves or radio waves
Microwaves are used extensively in communications
such as to relay long-distance telephone signals, television programs and computer information across the earth or to a satellite in space.
Good for transmitting information because it can penetrate haze, light rain and snow, clouds, and smoke.
Also used in radars and in detecting speeding cars.
Microwave has become most familiar as the energy source for cooking food.
Electromagnetic Spectrum
Electromagnetic radiation exists in a range of frequencies called the electromagnetic spectrum.
Each frequency has a specific wavelength and as the frequency decreases, the actual length of the wave gets longer.
Invented accidentally by Dr. Percy LeBaron Spencer
While testing a magnetron during work, he discovered the candy bar in his pocket melted
Experimented with other food products (popcorn and eggs), and realized microwaves can cook foods quickly
At 1947, 1st commercial microwave oven produced (called Radarange)
Mostly used by restaurants, railroad cars, ocean liners and military
Improvement and refinements made ~ by 1967, 1st domestic microwave oven produced
How the Oven Works
Electricity from the wall outlet travels through the power cord and enters the microwave oven through a series of fuse and safety protection circuits
These circuits include various fuses and thermal protectors that are designed to deactivate the oven in the event of an electrical short or if an overheating condition occurs
When the oven door is closed, an electrical path is also established through a series of safety interlock switches
The magnetron converts the high voltage in to the microwave frequency for cooking
The microwave energy is transmitted into a waveguide
The waveguide feeds the energy to the stirrer blade and into the cooking area
When the door is opened, or the timer reaches zero, the microwave energy stops.
How Foods Get Cooked
The microwaves that penetrate the food have an electric field that oscillates 2.45 billion times a second, a frequency that is well absorbed by polar liquid molecules such as water, sugars, fats and other food molecules.
Water interacts with the microwave:
flipping its orientation back and forth very rapidly
bumping into one another and producing heat, cooking the food.
Glass, paper, ceramic, or plastic containers are used in microwave cooking because the microwaves pass through them
Metal reflects microwaves
Unsafe to have metal pans/aluminum foil in oven, may damage oven
Health Hazards
It is known that microwave radiation can heat body tissue the same way it heats food.
Exposure to high levels of microwaves can cause a painful burn
Ex. the lens of the eye ~ exposure to high levels of microwaves can cause cataracts.
Microwave oven used low level of microwaves, within the region of non-ionizing radiation
Still uncertain in the effects of humans from long term exposure to low level of microwaves
Still experimenting
Best to stay a way (an arm’s length) in reducing exposure to microwaves

Important Note..!

If you are not satisfied with above reply ,..Please


So that we will collect data for you and will made reply to the request....OR try below "QUICK REPLY" box to add a reply to this page
Tagged Pages: flipping its orientation back and forth very rapidly bumping into one another and producing heat cooking the food, power point presentation of oven controlled crystal oscillator, radiation seminar topic microwave oven, microwave heating ppt, micro wave oven report pdf, microwave oven ppt, microwave ovan,
Popular Searches: seminar topics on micro oven, coke ovens and coal chemical plant, hyperphysics seminar topics microwave oven, working microwave oven ppt, weight measurement, energy conversion from one form to another, progme towards programmable network measurement,

Quick Reply
Type your reply to this message here.

Image Verification
Please enter the text contained within the image into the text box below it. This process is used to prevent automated spam bots.
Image Verification
(case insensitive)

Possibly Related Threads...
Thread Author Replies Views Last Post
  Worldwide Interoperability for Microwave Access pdf seminar projects maker 0 295 11-09-2013, 03:57 PM
Last Post: seminar projects maker
Last Post: study tips
  Microwave Photonics for Space Applications PPT study tips 0 455 10-05-2013, 04:28 PM
Last Post: study tips
  Microwave Devices PPT study tips 0 464 08-05-2013, 04:09 PM
Last Post: study tips
  Microwave Superconductivity seminarsense 4 5,394 11-03-2013, 10:31 AM
Last Post: study tips
  A Versatile Test Bench for Wireless RF/Microwave Component Characterization project girl 0 311 11-12-2012, 01:10 PM
Last Post: project girl
Last Post: seminar flower
  Mobile phone radiation and health’Case study: non-thermal effects of microwave ...... project uploader 0 866 28-07-2012, 01:19 PM
Last Post: project uploader
  MICROWAVE DEVICES seminar ideas 0 393 14-07-2012, 02:27 PM
Last Post: seminar ideas
  Solar Power Satellites and Microwave Power Transmission seminar surveyer 6 4,969 27-06-2012, 05:24 PM
Last Post: seminar flower