Transcript Microwaves Dave Klamer May 8, 2001 What is a “Microwave?” • Part of the RF spectrum – 1 - 300 GHz • A microwave oven 800-900

Microwaves
Dave Klamer
May 8, 2001
What is a “Microwave?”
• Part of the RF spectrum
– 1 - 300 GHz
• A microwave oven
800-900 MHz
50-600MHz
Uses of Microwaves
• Cooking
• Communication
– Radios
– Satellites
– RADAR
• Medicine
• Astronomy
How A Microwave Oven Works
Electricity flows from from the wall, through fuses
and safety mechanism to the controller
How A Microwave Oven Works
When the controller says to go, the triac activates, sending
power to the high voltage transformer (About 3000-4000 V)
How A Microwave Oven Works
• The magnetron tube
transforms the high voltage
into electromagnetic energy
• A waveguide guides the
microwaves into the
cooking chamber
• A stirring blade spreads
the microwaves evenly
High Voltage Components
• Several components needed
• The Magnetron is the heart
of the microwave
– 2450 MHz
• 2450 MHz happened to be available
• RF Leakage
Normal Microwave Use
• RF energy excites water
molecules
• Water molecules rotate on
poles, friction with
neighbor molecules
• Friction forces molecules
to retain energy, otherwise
it would just radiate
energy away
CD in Microwave
• RF energy bounces of from
CD, makes neat sparks
* This could cause damage to microwave
Lit Matchstick in Microwave
• Plasma of the fire rapidly
absorbs the large amount
of RF energy
* This may damage your microwave
Tinfoil in Microwave
• This is why your mom told
you to never put tinfoil in the
microwave!
• This kicks out a
tremendous amount
of heat and noise.
Will burn through
glass
Light Bulbs in Microwave
• A Christmas
treemake
ornament
works
much like
• Gasses
in light
bulb
it
glow
different
• A
laser
printer
lamp
a
CD,
but
in
a
3-D
Pattern
colors when subjected to microwave energy
• A small neon bulb works really well
The setup
At about 20sec
• A “burned
out” bulb will
work fine