[00:01.26]Unit 4 Inventions and Inventors
[00:05.02]Lesson 13
[00:10.56]Exercise 1.2
[00:14.46]Microwave ovens are used by
[00:16.53]millions of families every day.
[00:18.99]Many of you may have a microwave oven
[00:21.23]in your home.
[00:22.79]they are so simple to use.
[00:24.76]The food is placed in the oven.
[00:27.46]The oven is programmed for the correct time
[00:29.84]and then switched on.
[00:32.42]In just a few minutes,the food is heated
[00:35.22]and then taken out of the oven and served.
[00:37.97]Easy
[00:39.39]But do you know how a microwave oven works?
[00:42.58]Professor wilkins is here to explain.
[00:45.95]Well,it's quite simple,really.
[00:48.85]Micrwave ovens use microwaves to heat food.
[00:53.31]The microwaves are absorbed by the food and
[00:56.86]they are turned into heat.
[00:59.78]One advantage of microwave ovens is that
[01:01.98]they are very quick.
[01:03.96]Why is this?
[01:05.80]Microwave ovens can cook food quickly
[01:08.92]because all the food is heated at the same time
[01:13.29]And here's another questions for you.
[01:16.31]Why doesn't the plate get hot,
[01:18.43]when I cook something in my microwave?
[01:21.60]Ah,that is because
[01:23.87]the microwaves are absorbed by the food
[01:27.46]but they are not absorbed by things
[01:29.72]like plastic or glass.
[01:32.49]That is why plates and cups don't get hot.
[01:40.01]Exercise 2.2
[01:43.43]Today,photocopiers are found everywhere
[01:46.69]and millions of papers are copied every day.
[01:50.60]How does a photocopier work?
[01:52.94]An Original paper is placed face down
[01:55.88]on a special glass plate
[01:58.12]and the lid is closed.
[02:00.38]Different choices are chosen
[02:02.55]--for example,how many copies
[02:05.17]or what size of copy
[02:07.25]--and then the START button is pressed.
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