1、洗衣机来看一下涡流式全自动洗衣机的构造。这种洗衣机有各种各样的型号，其基本构造如图4.4 所示。 洗衣机之所以能兼具洗条和脱水的功能，是因为它有一个双层水槽。在积满水进行“洗条”和“漂洗”时，振动机旋转，产生水流。脱水时，只有内槽快速旋转，将衣服中的水甩出。最近渐渐流行的“ 离心式洗衣机 ”不是振动机旋转，而是内槽旋转。当内槽旋转时，该作用力使衣服贴近内层。由于水和洗条剂会从内槽的空洞向外甩出，因此能快速从衣服中穿透，用这种冲击力去除污后。这种机器的另一个好处是由于在水中衣物不会缠绕，因此不必担心衣物扭曲,变形或坏掉。 下面看一看不同类型的洗衣机！ 也许很多人认为洗衣机中的水是在以同样方式旋转
2、。事实上洗衣机的水流方式也有多种类型。 涡流式 这种类型洗衣机利用振动机的旋转产生涡流，从而祛除污后。有的新型洗衣机能使涡流上下反复旋转，从而使污后更容易祛除！ 搅拌式 这种洗衣机在底部有一个看起来像螺旋桨的带有叶片的轴，它会反复地反方向转动，将水搅动起来，然后水的作用力将衣物中的污后祛除。它具有使衣服不易缠绕，并能均匀清洗的优点。 滚筒式 在开有许多小孔的圆筒中，有突出的板子。外围的滚筒旋转时，板子将衣物抬起，下落是时的冲力将污后祛除。 离心力式 就像我们前边所说的那样，旋转的内槽将水和洗条剂从内槽壁推出。从内槽向外甩出的力叫做“离心力 ”，这也是 “离心力”这个名字的来源。这种洗衣机由于是
3、内槽旋转，因此水会从内槽猛地向外部喷射，然后又会回到内槽中，不断地循环往复。正是这种循环清洁了衣物！1930 年，在日本，人们第一次开始使用洗衣机。不过，当时的售价还很高，并没有普及到一般家庭。 在以前的洗衣机中，安装了现在看起来有些可笑的部件。机器有两根滚轴，夹住洗条衣物，把水挤出来。由于采用的是手动旋转把手后滚轴转动的构造，所以需要相当大的力气，不过在当时它还是非常便利，此后，这种滚轴式脱水机大约被使用了长达 30 年之久，一直到离心式脱水机出现为止。 1953 年,涡流式洗衣机的原形分流式洗衣机在日本上市销售。这种洗衣机就像现在所见的涡流式洗衣机的哥哥。由于这些洗衣机的价格低廉，使用洗衣
4、机的家庭渐渐多起来。1968年，全自动式洗衣机登场，此后洗衣机变得愈加方便了。 洗衣机有许多种类。你们家里用的洗衣机属于哪一种类型呢？ 全自动式 全自动式洗衣机通过双层的水槽接连进行洗条，漂洗，脱水。你需要做的就是将洗条剂和衣物放入洗衣机，之后洗衣机会自动进行清洗。还有一种可以烘干衣物的新型的全自动洗衣机。 双缸式 这种洗衣机进行洗条的部分与脱水的部分分离。虽然脱水时需要将衣物取出更换地方，但却具有洗条与脱水能同时进行的好处。 滚筒式 滚筒式洗衣机的特点是用水量较少，洗衣店使用的多是滚筒式的。许多欧洲家庭中也使用这种类型的洗衣机。 让我们制造出世界上最好的洗衣机！ 我们应该很感激科学家发明出全
5、自动洗衣机，因为它使洗衣服变成一件容易的事。 科学家仍在努力寻找方法使洗衣机的使用更加便利。另外，科学家们还正在努力，寻找更好的洗条衣物的方法和制造更耐用的洗衣机。现在洗衣机具有烘干功能，所以你甚至洗后不用进行挂晒，因为它可以自动烘干衣物！太神奇了！ 目前科学家正在想方设法减少洗衣时的用水量。其原因是我们必须珍惜水资源，保护我们的环境。 你认为未来的洗衣机将会变成什么样子呢？如果能有可以洗条，烘干，折叠衣物或是能在人穿着衣服时进行洗条的洗衣机的话，该有多方便啊！记住。 ，如果第一台洗衣机对旧时代的人们是一个梦想的话，那么对未来洗衣机的种种设想就很可能会变为现实。 让我们想一想。为什么冰箱会制冷
6、呢？如果先了解一下“汽化热” 这个词的意思，就会明白它的秘密了。 打针的时候，护士会在注射前用含有酒精的棉球檫拭你的手腕处，这会使你的手腕处有冰凉的感觉。那是因为液态的酒精在转变成气体时（汽化过程）将手腕皮肤的热量带走的缘故。这种热就叫做“ 汽化热 ”。 在炎热的夏天，往院子里洒上水就能变得凉快，也是因为汽化热作用。水带走了地面和空气中的热量，变成了水蒸气。 冰箱制冷利用的就是这种汽化热的交换作用。通过汽热化将食品的热量带走，从而使它变冷，并将热量排出。这就是冰箱的基本原理。汽化热是怎样产生的呢？ 冰箱的内部构造如图 4.5 所示。 如果沿着单向的箭头，就可以了解气体是以怎样的流向发生变化的。
7、靠近压缩机的箭头和其它的箭头描述了气体循环的情况。其各自的作用如下： 压缩机：对气体加压，使它变为液体。 冷却器：将热量排到冰箱外部。蒸发器：减压，将液体还原为气态。这时被带走的汽化热上冰箱冷却。 那么，冰箱是如何进行汽化热交换的呢？ 如仔细观察冰箱后部，会发现许多上下环绕的管子。实际上，冰箱除了门以外的部分，都遍部有充入气体的管子。这些管子里充满气体，当加压时会变成液体，减压时又会变成气体。在从液体转变为气体的同时，发生带走汽化热的交换作用。冰箱反复地进行着这种交换流程。 直到 20 世纪 90 年代末，冷却管内才开始使用替代氟利昂。但是由于发现以前使用的“替代氟利昂 ”对地球环境不利，所以
8、转而使用其他气体来代替。目前许多公司正在进一步开展“无氟冰箱 ”的制造，以更利于环境保护。 微波炉诞生于 20 世纪 40 年代末的美国。第二次世界大战期间，微波技术广泛应用在雷达设备上，因此这一技术也得到了提高。战后科学家们用这些知识发明了第一台微波炉。事实上正式由于这一历史原因，微波炉起初被叫做“ 雷达烤箱” 。在那段时间，由于微波炉体积庞大，只有餐馆和一些其他的行业使用。 20 世纪 60 年代，日本制造出第一台家用微波炉，但在当时只有富裕家庭才能买的起。而如今在许多国家人们都能买的起微波炉了。 有了微波炉，加热剩饭菜会变的十分简单。随着人们越来越多的了解使用微波炉所带来的便利，微波炉逐
9、渐得到了推广。接下来让我们了解一下微波炉是如何发展的。 微波炉是使用一种被叫做微波的电磁波（所以称微波炉）加热食物的。这种微波类似海洋中的水波。可以在 1 秒钟内振动高达 24 亿 5 千次。大多数食物中都含有水分。当水分子在经微波照射后会以非常快的速度振动。因此将微波照射到食物上后，食物中的水分子会通过振动相互碰撞，相互摩擦。摩擦产生的热叫摩擦热，而它使食物变热了。如果用火加热食物，会从外避开始逐渐变热，要加热至内部是需要一段时间的。而微波炉通过微波可以很快从食物内部开始加热。 让我们来研究一下微波炉的内部构造，看到图 4.8 中右上部的东西了吗？它就是微波炉内部被称作“ 磁控管” 的装置。
10、加热食物所用的微波，就是在这里产生的。发出的微波，通过波导管送入内部。 微波炉内壁由金属制成。这是因为如果微波第一次没有照到食物上，与内壁碰撞之后也会被弹回照到食物上。在门上覆盖有隔板，这样微波就不会泄漏到外部。 位于微波炉正中央的是转盘。是否注意到在用微波炉加热时，转盘总是会不停的旋转？ 微波通过波导管送入微波炉内部时，不管怎样总会有一些地方照到微波，而有些地方很难照到，产生出差异来。这样一来，即使对食物进行加热，也会使得有些地方热，有些地方凉。这样食物就不好吃了。 怎样才能将微波均匀地照射到食物上呢？科学家反复研究后发现，通过转动食物要比试图改变微波以使其均匀照射更容易解决这一问题。于是就
11、制作了转盘，将食物摆在上面旋转。看到过雪的结晶吗？将雪抓到受中时，有时可瞬间地看到它的形状，雪晶体呈现以六角形为基础。比如雪融化成水时就不在是结晶状态了。 大家知道物体有固态、液态、气态三种状态吧？大多数物体都只有这三种状态。但是某些物体在转化过程中还保持一种介于固态和液态之间的一种状态。在这种情况下，这种物体虽然以液体的形式存在，但仍然保留着规则有序的结晶状排列。 从很久以前，人们就了解了这一现象。这一现象得到广泛确认后，从 1889 年在德国发表了叫做“流动晶体 ”的研究报告，距今已经 100 多年了。经过长时间的研究和发表，液晶电视达到了目前的水平。 将钉子放在两块磁铁之间，钉子的两端会
12、向两块磁铁的方向靠近。与此相同，液晶并非成圆形，而是成细长形状，通电时具有与电流方向平行排列的性质。 在液晶电视机的屏幕中，两片玻璃之间有许多很小的间隔，分别在里面注入液晶，有红、蓝、绿三种颜色。由于平时液晶都在非活跃状态，所以即使有光线从屏幕后面照射过来也不会透光。 然而，当电流在蓝色间隔通过时，这个间隔中的液晶活跃起来，并透过光线。这就是画面怎样变成蓝色的缘故。混合红、蓝、绿（光的三原色）光后产生出各种颜色，这一点与显像管电视机相同，不过是液晶的光通过关闭或者特过光线而产生不同的颜色。 两片玻璃的间距仅为千分之五毫米。其空间只是头发的千分之一左右。在那里面装入液晶并让它按我们的要求运动是很
13、了不起的，而要把两片玻璃在如此小的空间中毫不弯曲地支撑起来就更了不起了。所以把液晶电视做成 30 英寸那么小是很难的。 由于这种技术基于开闭或打开光阀决定是否透光，因此生产液晶电视还存在一个难点，也就是从莫一角度看，屏幕会很暗，但人们找到了解决这些问题的方法，曾被认为不可能的液晶电视机也制造出来了。不知道当你成为大人的时候，什么样的液晶电视会存在你周围。washing machinesLets look inside one of todays fully automatic washing machines that use swirling water to clean the cloth
14、es. 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
15、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 quickl
16、y. 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. A
17、nother 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
18、. 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 t
19、his 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
20、 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
21、 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
22、 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,
23、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
24、 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 u
25、ntil 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 t
26、hese 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
27、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
28、 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
29、 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 w
30、ashing 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
31、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
32、 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 aft
33、er 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
34、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. W
35、hen 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
36、 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 i
37、s 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 si
38、ngle 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 int
39、o 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 e
40、very 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 refrige
41、rator. 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 companie
42、s 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 Us
43、ed 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 microw
44、ave 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 m
45、icrowave 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
46、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 fi
47、re 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 r
48、ight 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 mi
49、crowave 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 microwave
