A microwave oven, is a kitchen appliance that can come in many different sizes and styles employing microwave radiation primarily to cook or heat food. This is accomplished by using microwaves, almost always emitted from a magnetron, to excite water (primarily) and other polarized molecules within the food to be heated. This excitation is fairly uniform, leading to food being heated everywhere all at once

1. PRESENTATION
ON
MICROWAVE OVEN

2. Done By : Mumu Nafisa Tabassum
13-24539-2
Electronics Shop, Sec:G, Group 5
Electrical & Electronics Engineering
American International University
Bangladesh

3. CONTENTS
 INTRODUCTION
 INVENTION
 ABOUT MICROWAVE
 PRINCIPLE
 HOW IT WORKS
 APPLICATION
 EFFECTS OF MICROWAVE OVEN

4. INTRODUCTION
 A microwave oven, is a
kitchen appliance that can
come in many different sizes
and styles employing
microwave radiation
primarily to cook or heat
food. This is accomplished
by using microwaves, almost
always emitted from a
magnetron, to excite water
(primarily) and other
polarized molecules within
the food to be heated. This
excitation is fairly uniform,
leading to food being heated
everywhere all at once

5. Basic structure

6. History
 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

7. 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.

8. 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.
Radiation Type Frequency Range (Hz) Wavelength Range
Gamma rays above 3 x 1019 < 10-12 m
X-rays 3 x 1017 - 3 x 1019 1 nm - 1 pm
Ultraviolet Radiation 7.5 x 1014 - 3 x 1017 400 nm - 1 nm
Visible Spectrum 3.8 x 1014 - 7.5 x 1014 750 nm - 380 nm
Infrared Radiation 1011 - 3.8 x 1014 25 um - 2.5 um
Microwaves 108 - 1012 1 mm - 25 um
Radio waves 104 - 108 >1 mm
Table 1: Frequency and Wavelength Range of Each Radiation
Type in the Electromagnetic Spectrum.

9. PRINCIPLE
 Microwave oven works by passing non-ionizing microwave
radiation, usually at a frequency of 2.45 GHz (a wavelength of 12.24
cm), through the food. Microwave radiation is between common
radio and infrared frequencies. Water, fat, and other substances in the
food absorb energy from the microwaves in a process called dielectric
heating. Many molecules (such as those of water) are electric dipoles,
meaning that they have a positive charge at one end and a negative
charge at the other, and therefore rotate as they try to align
themselves with the alternating electric field of the microwaves. This
molecular movement creates heat as the rotating molecules hit other
molecules and put them into motion. Microwave heating is most
efficient on liquid water, and much less so on fats and sugars (which
have less molecular dipole moment), and frozen water (where the
molecules are not free to rotate). Microwave heating is sometimes
explained as a rotational resonance of water molecules, but this is
incorrect: such resonance only occurs in water vapor at much higher
frequencies, at about 20 gigahertz.

10.  Microwave oven uses
microwave radiation to heat
food in the subject inside the
oven
 microwave radiation are
radio waves with frequencies
2500 MHz and the radio
waves at this frequency has
an important property

11.  The food particles that contain water, fats and sugars
absorb microwave radiation through atoms and
molecules of food and absorption of this radiation gives
energy make the move significantly and collide and
produce heat for heating cooking
 That the material, plastic and glass, ceramics and pottery
does not absorb microwave radiation and is not affected,
and this means that they will not rise the temperature,
and the shiny metallic materials such as aluminum that
reflects the rays is therefore prohibited for use within
microwave ovens

12. In general, the
microwave oven
consists of two
main of operation:
 the control unit
 production unit
high voltage

13.  The microwave oven cook food
from the inside to outside
 Absorbs water and fat and sugar
molecules, consisting of food,
radio waves
 Temperature of food particles at
the same time and at the same
temperature because all the
particles are raised at the same
time is not transmitted to the
heat conduction

15. APPLICATION
•Microwave ovens are
popular for reheating
previously cooked foods
and cooking vegetables.
•They are also useful for
rapid heating of otherwise
slowly prepared cooking
items, such as hot butter,
fats, and chocolate.
the oven is used to heat
frying-oil and other very
oily items (such as bacon),
which attain far higher
temperatures than that of
boiling water.

16. HARMFUL EFFECTS
 CANCER CAUSING EFFECTS
 DECREASE IN NUTRITIVE VALUES
 BIOLOGICAL EFFECTS

17. CANCER CAUSING EFFECTS
 CANCEROUS CELLS IN BLOOD
 TUMORS
 CREATION OF AGENTS
 ELEMENTAL FOOD
 UNSAFE FOR BABY’S MILK

18. DECREASE IN NUTRITIVE VALUES
 DECREASE IN SOME TERMS OF
FOOD
 ENERGY CONTENTS
 NUCLEOPROTIENS

19. BIOLOGICAL EFFECTS
 DEGENERATION AND CIRCUIT
BREAKDOWNS.
 MICROWAVE SICKNESS.
 REPRODUCTIVE SYSTEM.
 HARMONES.

20. References
1. Dalhousie University, Halifax, Nova Scotia.
http://www.dal.ca/~ehs/files/microwave.safety.pdf
2. Homepage of Central Valley Christian School.
http://home.cvc.org/microwaves/
3. Nave, C. R. Hyperphysics. Georgia State University. http://hyperphysics.phy-
astr.gsu.edu/hbase/waves/magnetron.html
4. Microtech: The Complete Microwave Oven Repair and Information Network.
http://www.gallawa.com/microtech/index.html
5. Wright, Michael and Mukul Patel. Scientific American: How Things Work Today. New
York: Marshall Editions Development Ltd., 2000.