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washing machinesLets look inside one of todays fully automatic washing machines that use swirling water to clean the clothes. There are many types of washing machines but this Fig.4.4 shows you what most of them are basically made up of. The reason why a washing machine like this can wash and get the water out of the clothes at the same time is because it has a double layer drum. When washing and rinsing, the pulsator spins and makes the water swirl. To get the water out of the clothes, the inner wall f the drum spins and the water goes through the holes. These days, the “centrifugal force washing machines” are quite popular. This type of machine does not use a pulsator. Instead, the inner wall spins really quickly. When the drum spins, the dirty clothes get stuck to the wall. The water and detergent also try to escape through the holes of the wall but before they do so, they are forced to escape through the clothes. When this happens, the power of the water and detergent removes the dirt form the clothes. Another good thing about this type of machine is that clothes dont get tangled up so you dont have to worry about your clothes getting ripped or damaged. Next, lets look at some different types of washing machines! Many of you probably think that the water inside washing machines goes round and round. Actually, different washing machines make water flow in different ways. Whirlpool type This type of washing machine uses a pulsator to force the water to move like a whirlpool inside the Drum. The spinning water forces the dirt out form the clothes inside the machine. Some of the newer models of this type also make the whirlpool move up and down to make it clean clothes even better! Agitator stirring type This type of washing machine has something that looks like a propeller at the bottom of the tub. This Propeller spins around and stirs the water. The water then forces the dirt out from the clothes in the machine. The good thing about this type of machine is that clothes do not get tangled up and clothes get evenly washed. Drum type This type of machine has a drum with many holes in it. There are also protrusions bumps on the wall of the drum. As the drum turns, the clothes are picked up by the protrusions. When the clothes fall down from the top of the drum through the water, the movement removes dirt from the clothes. Centrifugal force type As we have said before, the spinning drum pushes the water and detergent out through the wall of the inner drum. The power that comes form spinning the drum is called centrifugal force., which is where the name comes from. The water is forced through the clothes and then the holes in the inner wall. After one cycle, the water is recycled back into the tank and the process starts again. This cycle is what cleans the clothes! In Japan, people first started using machines in 1930. But then the price of a washing machine was so high that most average persons could not buy one for their homes. Looking back now, there was something strange and funny on some of the first versions of the washing machine .The machine had two rollers that were used to sandwich each shirt and other clothes to squeeze the water out of them. The rollers were turned by hand, and in fact, you needed a lot of strength to turn those things! Still, people then thought it was a really neat invention! This type of water squeezer was used for almost 30 years until something new came along. The spin drier that used “centrifugal force” to get most of the water out of the clothes. In 1953, the nozzle type washing machine was first sold in Japan. This washing machine is like the older brother of the swirling washing machine that you see today. The price of these washing machines was lower and because of this, more people bought them. The first fully automatic washing machine was introduced in 1968, and after that, washing clothes became a lot easier to do! There are a lot of different types of washing machines. What kind of washing machine do you have in your house? Fully automatic: The fully automatic machine has two drum layers that wash, rinse and remove water from clothes together. All you have to do is add detergent and put in dirty clothes and then washing machine will do the rest. There is also a new type of fully automatic washing machine that can dry clothes after they have been washed. Twin tub: This washing machine has one part that dose the washing and another part that does the squeezing. Even though its a hassle to take the clothes out and move them to other tub, the good thing is that you can wash and squeeze at the same time with one machine. Front loading: The main feature of front loaders is that they use a lot less water than other types. This is the type of Washing machine that dry cleaners use but a lot of people in western countries have this type of washing machine in their homes too. Lets try to make the best washing machine in the world! We should already thank the scientists that invented the fully automatic washing machine because it makes washing clothes a piece of cake. Scientists are still trying really hard to find ways to make washing machines a lot handier to use for everyone. Some of the things that they are trying to do are to find better ways of making clothes clean and ways to make washing machines last longer. There are washing machines with d trying function today so you dont even have to hang clothes after words because it dries them automatically! Amazing! Scientists are also trying to find ways to use less water and less detergent in washing machines at present. This is because that it is better to use less water for preserving the environment. What are washing machines of the future going to be like? Maybe there will be a washing machine that dries and folds your clothes after washing them, or maybe there will be one that will wash your clothes while you are still wearing them! How handy would that be! Remember, if the first washing machine was like a dream to people in the old days, all the dreams you have about washing machines of the future may come true! Now, Lets try to figure out why refrigerators get cold. First, we should find out what vaporization heat is. One we know this, the rest is easy! When you go to the doctors to get your shots (injections), the nurse usually wipes alcohol on your arm with a cotton ball before she puts the needle into your arm. When she does that, that part of your arm feels really cool. The reason why it feels coll is that when liquid alcohol turns into vapor (a prcess called vaporization), it steals the heat away from the skin on that part of your arm. The heat leaving your skin is called vaporization heat. The reason why sprinkling water on your yard on a really hot summer day makes you feel cool is because of vaporization heat. The sprinkled water steals the heat away from the ground and air and turns into vapor. Refrigerators also exchange vaporization heat to become cool. The main way a refrigerator cools down is using vaporization heat to steal heat away from food and then taking it outside. How do you make (or induce) vaporization heat? The inside of the walls of a refrigerator looks like Fig.4.5. You will be able to figure out how he gas flows and where it changes from gas to liquid if you follow the single arrows (in the Fig.4.5). The arrow near the compressor and other arrows are what are used to move the gas around arrows means. Compressor: Squeezes the gas and turns it into liquid. Condenser: Takes the heat away from the refrigerator. Evaporator: Takes the pressure away to turn liquid back into gas. The vaporization heat taken heat taken away at this point is what cools the refrigerator. Now lets try to figure out how refrigerators exchange vaporization heat. If you look closely at the back of a refrigerator, you will find a lot of tubes that go up and down. These tubes are attached to every wall, except the door of course. These tubes have gas in them and when the gas is squeezed (or compressed), it turns into liquid. When it is released, the liquid turns into gas again. When the gas changes from liquid back to gas again, vaporization heat is removed from the inside of the refrigerator. This process is repeated over and over all day long. Until the late 1990s, chlorofluoro methane carbon (CFC) gas was used inside the tubes. But scientists found out that CFCs were actually bad for the environment and nowadays, a different gas is being used more and more instead. Many companies are now trying to make refrigerators that are CFC free so that they are better for the environment. The microwave oven was invented in the late 1940s in the US. During World War II, microwave.Technology was used a lot in radar equipment, so the technology was advanced. After the war, scientists Used the knowledge that they had of microwaves to invent the first microwave oven. In fact, the microwave oven was called a “radar oven” at first because of its history. Back then, microwave ovens were so big that only restaurants and other businesses used them. In the 1960s, the first home-use microwave oven was made in Japan. In those days, only rich people could afford it, but now a day , microwave ovens are more affordable for people in many countries. It is easy to heat up yesterdays leftovers with a microwave oven. As people like you start to understand more about how easy and convenient microwave ovens are, their popularity grow. Next, lets look at how microwave ovens have changed over time. Microwave ovens heat up food using electromagnetic waves called microwave (hence the name). These microwaves oscillate (go up and down like a wave in the ocean) 2,400,005,000(2.4 billion) times every second! Most food contains water. When microwaves hit molecules of water, the molecules start vibrating really fast, which makes the water molecules hit each other and rub against each other. Heat caused by rubbing is called “frictional heat and this what starts cooking the food. If you use fire to heat something, it starts to get hot from the outside and it takes some time before the inside gets hot. But because microwave ovens use the power of microwaves, they can start cooking food from the inside right away. Lets take a look inside a microwave oven. Do you see that thing at the top right of the Fig.4.8? That is what is called a magnetron. This device makes the microwaves that heat and cook your food. The microwaves enter the oven area by traveling through a tube called a wave -guide. The inner wall is made of metal wall hit your food, even if they miss it the first time. The microwave door has a special oven on it that stops microwaves from escaping outside. In the middle of the microwave oven is the turntable. Do you notice that when you heat something in a microwave oven, the turntable is always turning? When the wave-guide tube we talked about before injects microwaves into the inside of a microwave oven, there are always some areas that get hit with a lot of waves and some areas that dont. If food was warmed up like that, there would be parts that were hot and parts that were cold, so the food wouldnt taste too good. How do you get the microwaves to hit all parts of the food evenly? Scientists mulled over this question for a very long time and realized that moving the food was a lot easier than trying to make the microwaves reach every corner of the oven evenly. Thats why scientists started using turntables to spin the food inside microwave ovens. Have you ever seen a snow crystal? Sometimes its possible to see them for a short moment when snow lands on your hand, but most of the time it melts before you get to see the beautiful hexagon-shaped (six said) crystals. Crystals are made up of particles that are arranged in a regular its crystal shape. Do you know that there are three states for most objects: solid, liquid and gas? Most things only come in these three forms. However, some material can remain in a state that is somewhat between a solid and a liquid, In this state, the object is a liquid but still maintains the regular crystal like arrangement. The existence of this state has been known for a very long time. In fact, there was a research article titled “the flowing crystal “ that was published in 1889, over 100 years ago. It took many, many years of research and development to get liquid-crystal display TVs to the point that they are at now. If you put a nail in the middle of two magnets, the ends of the nail try to point towards each magnet. Similarly, crystals do not have a round shape but have a long narrow shape and when electricity is passed through a crystal, it tries to align itself in the direction of the electrical flow. In a Liquid crystal TV, many small compartments are left between two pieces of glass. Each of these Compartments holds liquid crystals that are colored red, blue or green. Even if light is shined on the back of the screen