Unit 4 Inventions and Inventors Lesson 13 Exercise 1.2 Microwave ovens are used by millions of families every day. Many of you may have a microwave oven in your home. they are so simple to use. The food is placed in the oven. The oven is programmed for the correct time and then switched on. In just a few minutes,the food is heated and then taken out of the oven and served. Easy But do you know how a microwave oven works? Professor wilkins is here to explain. Well,it's quite simple,really. Micrwave ovens use microwaves to heat food. The microwaves are absorbed by the food and they are turned into heat. One advantage of microwave ovens is that they are very quick. Why is this? Microwave ovens can cook food quickly because all the food is heated at the same time And here's another questions for you. Why doesn't the plate get hot, when I cook something in my microwave? Ah,that is because the microwaves are absorbed by the food but they are not absorbed by things like plastic or glass. That is why plates and cups don't get hot. Exercise 2.2 Today,photocopiers are found everywhere and millions of papers are copied every day. How does a photocopier work? An Original paper is placed face down on a special glass plate and the lid is closed. Different choices are chosen --for example,how many copies or what size of copy --and then the START button is pressed.
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