MicrowavesMicrowaves

How long have microwaves been How long have microwaves been around?around?

In 1945, Dr. Perry Spencer, a scientist, In 1945, Dr. Perry Spencer, a scientist, was working in a lab when he felt some was working in a lab when he felt some heat on his hand. The heat was coming heat on his hand. The heat was coming from microwaves. These were being from microwaves. These were being emitted from a nearby vacuum tube. Dr. emitted from a nearby vacuum tube. Dr. Spencer was curious and place a Spencer was curious and place a chocolate bar near the tube. Within chocolate bar near the tube. Within seconds, the chocolate melted. That sticky seconds, the chocolate melted. That sticky mess was the beginning of a brilliant idea mess was the beginning of a brilliant idea – the microwave!– the microwave!

Diagram of MicrowaveDiagram of Microwave

How Does a Microwave Work?How Does a Microwave Work? The microwave oven generates electromagnetic The microwave oven generates electromagnetic

waves (called microwaves) which makes water waves (called microwaves) which makes water move. This motion leads to friction, and friction move. This motion leads to friction, and friction leads to heating. leads to heating.

Motion Friction Heat

How Does a Microwave Work?How Does a Microwave Work?

This heat starts on the outside of the food This heat starts on the outside of the food and moves in.and moves in.

The denser the food the longer it will take The denser the food the longer it will take to cook.to cook. Water will heat faster than a burrito, because Water will heat faster than a burrito, because

a burrito is more dense than water.a burrito is more dense than water.

What are the advantages of having What are the advantages of having a microwave?a microwave?

FasterFaster Retains NutrientsRetains Nutrients Tastes BetterTastes Better Defrost MeatDefrost Meat Softens brown sugar (Put 1C. of water in microwave)Softens brown sugar (Put 1C. of water in microwave) Plumps RaisinsPlumps Raisins Freshens snacks and chipsFreshens snacks and chips Eliminates extra oils and fats in preparing foodsEliminates extra oils and fats in preparing foods Made a impacted on today’s lifestyle and cooking habitsMade a impacted on today’s lifestyle and cooking habits Cook’s food quickly with high qualityCook’s food quickly with high quality

What are microwaves attracted to?What are microwaves attracted to?

FatFat SugarSugar Water MoleculesWater Molecules

Acceptable dishes for the Acceptable dishes for the microwavemicrowave

GlassGlass PaperPaper PlasticPlastic Microwaveable DishesMicrowaveable Dishes

Unacceptable DishesUnacceptable Dishes MetalMetal Dishes with gold or Dishes with gold or

silver on itsilver on it

Acceptable CoveringsAcceptable Coverings Paper Towels- Paper Towels- to to

absorb moisture, absorb moisture, spatters, and spillsspatters, and spills

Wax Paper-Wax Paper- Holds in Holds in some of the moisturesome of the moisture

Plastic Wrap-Plastic Wrap- holds holds in moisturesin moistures

Foods that should not be Foods that should not be microwavedmicrowaved

EggsEggs in a shell in a shell PancakesPancakes-they don’t get a -they don’t get a

crust on them.crust on them. Canning foodsCanning foods -does not get -does not get

high enough temperature or high enough temperature or have enough pressure.have enough pressure.

Deep-fry foods-Deep-fry foods- fat can not be fat can not be controlledcontrolled

Large amounts of food-Large amounts of food- Takes to long, not as efficientTakes to long, not as efficient

TechniquesTechniques StirringStirring: To pull heated part of the food to the : To pull heated part of the food to the

center.center. Turning OverTurning Over: To microwave all sides.: To microwave all sides. Standing timeStanding time: To allow the foods to complete : To allow the foods to complete

its cooking (place directly on counter).its cooking (place directly on counter). ShieldingShielding: Small pieces : Small pieces CoveringCovering: :

A: Retains nutrientsA: Retains nutrients B. Holds in moistureB. Holds in moisture C. Speeds up cookingC. Speeds up cooking

Arrange food in circular shape:Arrange food in circular shape: to make to make cooking evencooking even

RotatingRotating: Makes cooking even: Makes cooking even PrickingPricking: (egg yolks and potatoes) to : (egg yolks and potatoes) to

keep from exploding.keep from exploding. Select foods of the same sizeSelect foods of the same size: cooks : cooks

evenlyevenly

Do round or square containers cook more Do round or square containers cook more evenly?evenly?

RoundRound Square

BurnsBurns

To preventTo prevent Food can create hot containersFood can create hot containers Items can explode (egg, potatoes). Pierce Items can explode (egg, potatoes). Pierce

them with fork.them with fork. Lifting the cover or plastic from the food can Lifting the cover or plastic from the food can

cause a burn.cause a burn. Hot steam escaping can cause a burn.Hot steam escaping can cause a burn.

Cooking TipsCooking Tips

When cooking in the microwave, the When cooking in the microwave, the volume of the food (small versus large volume of the food (small versus large potatoes); and the quantity or number will potatoes); and the quantity or number will increase cooking and standing time.increase cooking and standing time.

Standing time at the end of cooking allows Standing time at the end of cooking allows for foods to continue to cook when for foods to continue to cook when removed. removed.

SuperheatingSuperheating

http://www.phys.unsw.edu.au/~jw/superheating.html

http://www.colorado.edu/physics/2000/microwaves/index.html

Learning how microwaves works.Learning how microwaves works.