Microwaves

Dave Klamer

May 8, 2001

What is a “Microwave?”• Part of the RF spectrum

– 1 - 300 GHz• A microwave oven

800-900 MHz50-600MHz

Uses of Microwaves

• Cooking

• Communication– Radios– Satellites– RADAR

• Astronomy

• Medicine

How A Microwave Oven WorksElectricity flows from from the wall, through fuses

and safety mechanism to the controller

How A Microwave Oven WorksWhen the controller says to go, the triac activates, sending

power to the high voltage transformer (About 3000-4000 V)

How A Microwave Oven Works

• A waveguide guides the microwaves into the cooking chamber

• The magnetron tube transforms the high voltage into electromagnetic energy

• 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 “burned out” bulb will work fine

• Gasses in light bulb make it glow different colors when subjected to microwave energy

• A small neon bulb works really wellThe setup At about 20sec

• A laser printer lamp• A Christmas tree ornament works much like

a CD, but in a 3-D Pattern