1、洗衣機來看一下渦流式全自動洗衣機的構造。這種洗衣機有各種各樣的型號，其基本構造如圖4.4所示。 洗衣機之所以能兼具洗條和脫水的功能，是因為它有一個雙層水槽。在積滿水進行“洗條”和“漂洗”時，振動機旋轉，產生水流。脫水時，只有內槽快速旋轉，將衣服中的水甩出。 最近漸漸流行的“離心式洗衣機”不是振動機旋轉，而是內槽旋轉。當內槽旋轉時，該作用力使衣服貼近內層。由于水和洗條劑會從內槽的空洞向外甩出，因此能快速從衣服中穿透，用這種沖擊力去除污后。這種機器的另一個好處是由于在水中衣物不會纏繞，因此不必擔心衣物扭曲,變形或壞掉。 下面看一看不同類型的洗衣機！ 也許很多人認為洗衣機中的水是在以同樣方式旋轉。事

2、實上洗衣機的水流方式也有多種類型。 渦流式 這種類型洗衣機利用振動機的旋轉產生渦流，從而祛除污后。有的新型洗衣機能使渦流上下反復旋轉，從而使污后更容易祛除！ 攪拌式 這種洗衣機在底部有一個看起來像螺旋槳的帶有葉片的軸，它會反復地反方向轉動，將水攪動起來，然后水的作用力將衣物中的污后祛除。它具有使衣服不易纏繞，并能均勻清洗的優點。 滾筒式 在開有許多小孔的圓筒中，有突出的板子。外圍的滾筒旋轉時，板子將衣物抬起，下落是時的沖力將污后祛除。 離心力式 就像我們前邊所說的那樣，旋轉的內槽將水和洗條劑從內槽壁推出。從內槽向外甩出的力叫做“離心力”，這也是“離心力”這個名字的來源。這種洗衣機由于是內槽旋轉

3、，因此水會從內槽猛地向外部噴射，然后又會回到內槽中，不斷地循環往復。正是這種循環清潔了衣物！ 1930年，在日本，人們第一次開始使用洗衣機。不過，當時的售價還很高，并沒有普及到一般家庭。 在以前的洗衣機中，安裝了現在看起來有些可笑的部件。機器有兩根滾軸，夾住洗條衣物，把水擠出來。由于采用的是手動旋轉把手后滾軸轉動的構造，所以需要相當大的力氣，不過在當時它還是非常便利，此后，這種滾軸式脫水機大約被使用了長達30年之久，一直到離心式脫水機出現為止。 1953年,渦流式洗衣機的原形分流式洗衣機在日本上市銷售。這種洗衣機就像現在所見的渦流式洗衣機的哥哥。由于這些洗衣機的價格低廉，使用洗衣機的家庭漸漸多

4、起來。1968年，全自動式洗衣機登場，此后洗衣機變得愈加方便了。 洗衣機有許多種類。你們家里用的洗衣機屬于哪一種類型呢？ 全自動式 全自動式洗衣機通過雙層的水槽接連進行洗條，漂洗，脫水。你需要做的就是將洗條劑和衣物放入洗衣機，之后洗衣機會自動進行清洗。還有一種可以烘干衣物的新型的全自動洗衣機。 雙缸式 這種洗衣機進行洗條的部分與脫水的部分分離。雖然脫水時需要將衣物取出更換地方，但卻具有洗條與脫水能同時進行的好處。 滾筒式 滾筒式洗衣機的特點是用水量較少，洗衣店使用的多是滾筒式的。許多歐洲家庭中也使用這種類型的洗衣機。 讓我們制造出世界上最好的洗衣機！ 我們應該很感激科學家發明出全自動洗衣機，因

5、為它使洗衣服變成一件容易的事。 科學家仍在努力尋找方法使洗衣機的使用更加便利。另外，科學家們還正在努力，尋找更好的洗條衣物的方法和制造更耐用的洗衣機。現在洗衣機具有烘干功能，所以你甚至洗后不用進行掛曬，因為它可以自動烘干衣物！太神奇了！ 目前科學家正在想方設法減少洗衣時的用水量。其原因是我們必須珍惜水資源，保護我們的環境。 你認為未來的洗衣機將會變成什么樣子呢？如果能有可以洗條，烘干，折疊衣物或是能在人穿著衣服時進行洗條的洗衣機的話，該有多方便啊！記住。，如果第一臺洗衣機對舊時代的人們是一個夢想的話，那么對未來洗衣機的種種設想就很可能會變為現實。 讓我們想一想。為什么冰箱會制冷呢？如果先了解一

6、下“汽化熱”這個詞的意思，就會明白它的秘密了。 打針的時候，護士會在注射前用含有酒精的棉球檫拭你的手腕處，這會使你的手腕處有冰涼的感覺。那是因為液態的酒精在轉變成氣體時（汽化過程）將手腕皮膚的熱量帶走的緣故。這種熱就叫做“汽化熱”。 在炎熱的夏天，往院子里灑上水就能變得涼快，也是因為汽化熱作用。水帶走了地面和空氣中的熱量，變成了水蒸氣。 冰箱制冷利用的就是這種汽化熱的交換作用。通過汽熱化將食品的熱量帶走，從而使它變冷，并將熱量排出。這就是冰箱的基本原理。汽化熱是怎樣產生的呢？ 冰箱的內部構造如圖4.5所示。 如果沿著單向的箭頭，就可以了解氣體是以怎樣的流向發生變化的。靠近壓縮機的箭頭和其它的箭

7、頭描述了氣體循環的情況。其各自的作用如下： 壓縮機：對氣體加壓，使它變為液體。 冷卻器：將熱量排到冰箱外部。蒸發器：減壓，將液體還原為氣態。這時被帶走的汽化熱上冰箱冷卻。 那么，冰箱是如何進行汽化熱交換的呢？ 如仔細觀察冰箱后部，會發現許多上下環繞的管子。實際上，冰箱除了門以外的部分，都遍部有充入氣體的管子。這些管子里充滿氣體，當加壓時會變成液體，減壓時又會變成氣體。在從液體轉變為氣體的同時，發生帶走汽化熱的交換作用。冰箱反復地進行著這種交換流程。 直到20世紀90年代末，冷卻管內才開始使用替代氟利昂。但是由于發現以前使用的“替代氟利昂”對地球環境不利，所以轉而使用其他氣體來代替。目前許多公司

8、正在進一步開展“無氟冰箱”的制造，以更利于環境保護。 微波爐誕生于20世紀40年代末的美國。第二次世界大戰期間，微波技術廣泛應用在雷達設備上，因此這一技術也得到了提高。戰后科學家們用這些知識發明了第一臺微波爐。事實上正式由于這一歷史原因，微波爐起初被叫做“雷達烤箱”。在那段時間，由于微波爐體積龐大，只有餐館和一些其他的行業使用。 20世紀60年代，日本制造出第一臺家用微波爐，但在當時只有富裕家庭才能買的起。而如今在許多國家人們都能買的起微波爐了。 有了微波爐，加熱剩飯菜會變的十分簡單。隨著人們越來越多的了解使用微波爐所帶來的便利，微波爐逐漸得到了推廣。接下來讓我們了解一下微波爐是如何發展的。

9、微波爐是使用一種被叫做微波的電磁波（所以稱微波爐）加熱食物的。這種微波類似海洋中的水波。可以在1秒鐘內振動高達24億5千次。大多數食物中都含有水分。當水分子在經微波照射后會以非常快的速度振動。因此將微波照射到食物上后，食物中的水分子會通過振動相互碰撞，相互摩擦。摩擦產生的熱叫摩擦熱，而它使食物變熱了。如果用火加熱食物，會從外避開始逐漸變熱，要加熱至內部是需要一段時間的。而微波爐通過微波可以很快從食物內部開始加熱。 讓我們來研究一下微波爐的內部構造，看到圖4.8中右上部的東西了嗎？它就是微波爐內部被稱作“磁控管”的裝置。加熱食物所用的微波，就是在這里產生的。發出的微波，通過波導管送入內部。 微波

10、爐內壁由金屬制成。這是因為如果微波第一次沒有照到食物上，與內壁碰撞之后也會被彈回照到食物上。在門上覆蓋有隔板，這樣微波就不會泄漏到外部。 位于微波爐正中央的是轉盤。是否注意到在用微波爐加熱時，轉盤總是會不停的旋轉？ 微波通過波導管送入微波爐內部時，不管怎樣總會有一些地方照到微波，而有些地方很難照到，產生出差異來。這樣一來，即使對食物進行加熱，也會使得有些地方熱，有些地方涼。這樣食物就不好吃了。 怎樣才能將微波均勻地照射到食物上呢？科學家反復研究后發現，通過轉動食物要比試圖改變微波以使其均勻照射更容易解決這一問題。于是就制作了轉盤，將食物擺在上面旋轉。 看到過雪的結晶嗎？將雪抓到受中時，有時可瞬

11、間地看到它的形狀，雪晶體呈現以六角形為基礎。比如雪融化成水時就不在是結晶狀態了。 大家知道物體有固態、液態、氣態三種狀態吧？大多數物體都只有這三種狀態。但是某些物體在轉化過程中還保持一種介于固態和液態之間的一種狀態。在這種情況下，這種物體雖然以液體的形式存在，但仍然保留著規則有序的結晶狀排列。 從很久以前，人們就了解了這一現象。這一現象得到廣泛確認后，從1889年在德國發表了叫做“流動晶體”的研究報告，距今已經100多年了。經過長時間的研究和發表，液晶電視達到了目前的水平。 將釘子放在兩塊磁鐵之間，釘子的兩端會向兩塊磁鐵的方向靠近。與此相同，液晶并非成圓形，而是成細長形狀，通電時具有與電流方向

12、平行排列的性質。 在液晶電視機的屏幕中，兩片玻璃之間有許多很小的間隔，分別在里面注入液晶，有紅、藍、綠三種顏色。由于平時液晶都在非活躍狀態，所以即使有光線從屏幕后面照射過來也不會透光。 然而，當電流在藍色間隔通過時，這個間隔中的液晶活躍起來，并透過光線。這就是畫面怎樣變成藍色的緣故。混合紅、藍、綠（光的三原色）光后產生出各種顏色，這一點與顯像管電視機相同，不過是液晶的光通過關閉或者特過光線而產生不同的顏色。 兩片玻璃的間距僅為千分之五毫米。其空間只是頭發的千分之一左右。在那里面裝入液晶并讓它按我們的要求運動是很了不起的，而要把兩片玻璃在如此小的空間中毫不彎曲地支撐起來就更了不起了。所以把液晶電

13、視做成30英寸那么小是很難的。 由于這種技術基于開閉或打開光閥決定是否透光，因此生產液晶電視還存在一個難點，也就是從莫一角度看，屏幕會很暗，但人們找到了解決這些問題的方法，曾被認為不可能的液晶電視機也制造出來了。不知道當你成為大人的時候，什么樣的液晶電視會存在你周圍。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

14、 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

15、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 g

16、et 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 machin

17、e 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

18、 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 an

19、d 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 abo

20、ut 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 fa

21、ll 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 fo

22、rce., 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

23、. 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

24、 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 dri

25、er 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

26、 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 a

27、utomatic 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

28、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

29、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 alre

30、ady 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 bett

31、er 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 de

32、tergent 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

33、 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 col

34、d. 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 fe

35、els 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

36、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 awa

37、y 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 nea

38、r 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 tak

39、en 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

40、 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 ov

41、er 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

42、 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 microwave

43、s 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,

44、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.

45、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. Whe

46、n 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

47、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

48、 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

49、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

50、 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 ove

51、r 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 po

52、ssible 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 mo

53、st 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 b

54、een 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 shap