Percy Spencer discovered microwaves in 1946 when a chocolate bar in his pocket melted after being exposed to magnetron waves. Microwaves work by causing water, proteins, and fats in food to vibrate, generating heat. The rotating plate in microwaves ensures even cooking by redistributing the microwaves. Metals and some plastics cannot be microwaved as they could generate electric currents or sparks due to microwave-induced heating.

1. 
MICROWAVES

2. 
 It was discobered by accident by Percey Spencer in
1946.
 He was working with a magnetron, and a chocalate
in his poquet started to melt.
 This was because of the high frequency waves this
object made.
History

3. 
 First we should say that we measure heat by the speed of
the vibrations an object makes.
 The magnetron( electronic valve) is a device that
produces microwaves
 Food has water, proteins, fats.. and it absorbs this waves
 This make the food start to vibrate, and produces heat.
HOW IT WORKS?

4. 
How it works?

5. 
 Why do they have a rotating plate?
Questions?

6. 
 Why can´t we put metals or plastics?
 Metals conduct heat and electricity, so there would
be a current in the object.
 This could cause electric rays.
Questions?

7. 
 https://youtu.be/FGdwEPEU61U
 https://youtu.be/BCVmSKS_LRw
Short video