大学英语 学英语,练听力,上听力课堂! 注册 登录
关闭

如果碰到什么问题,
您可以添加微信客服,进行咨询

> 公共英语 > 公共英语考试教程 > 全国英语等级考试教材第三级 >  第18课

全国英语等级考试教材第三级Unit18

所属教程:全国英语等级考试教材第三级

浏览:

gewei

手机版
扫描二维码方便学习和分享

https://online2.tingclass.net/lesson/shi0529/0008/8646/2/9.mp3
https://image.tingclass.net/statics/js/2012

[00:00.00] Chapter 18 Popular science

[00:12.59]Unit 18 Popular Science

[00:18.55]Conversations

[00:22.02]1.Tang Ming and Du Hua,two college students,are discussing computer craze.

[00:29.78]Now,Many students have computers.

[00:35.34]A computer craze has hit the campus of many colleges of China.

[00:41.59]yes,you are right.

[00:45.06]If you enter a dormitory,You will find one or two computers there.

[00:51.02]It is true that the computer has been used widely in students' studies.

[00:57.68]But some students often play computer games.

[01:03.24]Rigth.according to the survey,

[01:07.68]computers greatly influence some students' studies.

[01:12.96]In my university,

[01:16.30]many young video addicts could indulge themselves in games all night long.

[01:22.86]Oh.Fortunately,many universities and colleges are aware of such problems

[01:30.51]and are planning to carry out projects to correct this phenomenon.

[01:36.86]It seems to me that the campus computer problems

[01:41.93]are not a question of the computer itself but of the way of using it.

[01:47.78]I agree.

[01:50.84]We are sure tha tcolleges and universities can find a good solution to these problems.

[01:58.49]2. Wu Li is a salesman. Ma Gang is a customer.

[02:04.84]They are talking about exchanging a computer.

[02:09.38]What can I do for you?

[02:13.33]I bought a computer here last Friday and now it simply does not work.

[02:19.57]What's wrong with it?

[02:23.12]I'm not sure.

[02:26.18]When I turn it on,there's only sould but no words.

[02:31.51]Is the screen clear? Not very clear.

[02:36.34]Did you try it here before you took it home?

[02:41.49]yes.It was all right.

[02:45.15]But when it got to my office,it didn't work properly.

[02:50.11]It's unreasonalbe.

[02:53.95]Can you replace it with another one?

[02:57.89]I'm afraid not.

[03:01.37]Would you send the computer in and we have it checked first?

[03:07.53]Then we'll see what we can do about it.

[03:11.29]3. Tom and Susan are in Tom's sports car.

[03:17.54]They are at a petrol station.

[03:21.40]Three gallons of super,please.

[03:25.66]Three gallons of super.Yes,sir.

[03:29.92]Tom...why don't we get small family car?

[03:35.38]What? You mean,sell my sports car? Never!

[03:40.53]But it's expensive to run and it's old.

[03:46.17]You bought it long before.

[03:50.30]Er...excuse me.That's $5.sir.

[03:55.26]here you are.Oh,and would you check my battery,please?

[04:00.59]Check the battery,sir? Certainly.

[04:04.45]Don't you remember?

[04:07.98]It broke down just before we got married

[04:13.23]and it was in the garage for a whole week!

[04:17.99]This is a wonderful car! It always starts first time!

[04:23.34]The battery's all right,sir. Thank you.

[04:28.09]It didn't start first time yesterday morning!

[04:33.42]That was only because it was so cold!

[04:37.66]It's a wonderful engine.just listen to it when I start now!

[04:42.91](Presses starter.Sound of engine turning over but not starting.)

[04:49.46]I'm listening,Tom.

[04:53.62]Passage Electricity

[04:58.58] If you were thirsty,and took a cup to the kitchen sink,

[05:04.04]you might first turn the tap on just a little way,

[05:09.39]so that only a thin stream of water came form it.

[05:14.75]Then you would turn the tap a bit farther.

[05:19.79]Not only would there be more water,but also it would come out with greater force.

[05:27.84]If you turned it on as far as it would go ,

[05:32.90]you would get no water in your cup at all,

[05:37.66]for it would come form the tap in so powerful a jet

[05:43.41]that it would bounce straight out of the cup again,

[05:48.16]and most likely drench you.

[05:52.52] In that stream of water,then,are three things--

[05:58.09]or rather,two things and their result.

[06:03.55]Firstly,the amount or quantity,or current of water.

[06:10.42]Secondly,the pressure pushing it.

[06:15.46]And thirdly,the power of the jet,which is the result,

[06:21.62]or pruduct of the current of water and the force pushing it.

[06:27.68]Electrical power

[06:31.44] Although this is not quite the same as in electricity,

[06:37.40]it helps in understanding amps,volts and watts.

[06:43.46]For the volt is the unit of electrical pressure,or force.

[06:49.84]The amp (short for ampere) is the unit of electrical current,

[06:56.97]while the watt is the unit of electrical power.

[07:01.93] A watt is the power given by an ampere of current

[07:07.86]flowing in a circuit at a pressure of one volt.

[07:13.01]So the more the volts and amps there are,the more watts.

[07:19.85]As in that water tap,the more current there is,

[07:25.41]and the more pressure,then the greater the resulting power.

[07:31.34] The word "pressure" is not auite correct,however,when used about volts.

[07:38.81]They are better described as units of force--

[07:44.07]scientists and engineers cal them units of "electromotive force",or E.M.F.

[07:54.23] Resistance

[07:58.20] When you pump up your bicycle tyre,you use force,or pressure,

[08:04.96]to push air into the inner tube.

[08:09.51]But the air in there already pushes back against you.

[08:15.88]In much the same way,when you push a current of electricity through a wire,

[08:23.43]there is a kind of push-back,called "resistance",

[08:29.20]set up by the metal of which the wire is made.

[08:34.25] Just as the units of force,current and power ahve names,

[08:40.91]so has the unit of electrical resistance.It is called the "ohm".

[08:48.27]Resistance of metals

[08:52.35]Every metal ahs its own resistance to the passage of an electrical current through it.

[08:59.90]The lower the resistance of a metal,the better it is as a carrier,

[09:06.66]or "conductor" of electrical energy.

[09:11.63]For if you have to use up power in overcoming this resistance,

[09:17.98]there is so much the less for you at the other end of the conductor.

[09:24.24] The length of pieces of wire of the same diameter,

[09:29.89]each piece having a resistance of one ohm,

[09:35.45]will depend on the metal of which they are made.

[09:40.49]Again,for the same diameter,

[09:45.04]a wire of low resistance will be longer than one of high resistance.

[09:51.99]A copper wire will be longer than one of iron,

[09:57.73]or lead,or nickedl,for its resistance is very low,

[10:03.69]and not much energy is needed to overcome it.

[10:08.65] For this reason copper is used in making wires,

[10:14.53]cables and overhead lines for carrying electrical current.

[10:20.59] Aluminium is another good conductor with a low resistance.

[10:26.83]Being light in weight,it is often used for overhead lines,

[10:33.08]such as you see slung in graceful curves between pylons,

[10:39.14]but being a soft metal it usually has a steel wire core to give it strength.

[10:46.50] Sometimes,however,wires of high resistance are put to special uses.

[10:54.37]When electrical energy is taken up in overcoming the resistance of a wire,

[11:01.42]it produces heat.

[11:05.08]this makes the sire redhot,as in an electric radiator,

[11:11.74]or while-hot,as in the filament of a lamp.

[11:16.91]Thus from metals of high resistance,we can get either heat or light for our use.

[11:25.37]Words and Expressions

[11:29.03]thirsty tap bounce

[11:31.71]adj.口渴的 n.龙头 v.弹出

[11:34.39]drench amp volt

[11:36.71]v.使浸透,弄湿 n.(电)安培 n.(电)伏特,伏

[11:39.04]watt circuit pump

[11:41.41]n.(电)瓦特 n.电路;线路 v.为...打气

[11:43.79]wire resistance ohm

[11:46.17]n.电线 n.(电)电阻 n.(电阻单位)欧姆

[11:48.55]conductor diameter lead

[11:51.28]n.(电)导体 n.直径 n.铅

[11:54.00]nickel cable aluminium

[11:56.43]n.镍 n.(电)电缆 n.铝

[11:58.86]sling pylon

[12:00.90]v.吊 n.架高压电缆的铁塔

[12:02.94]radiator filament

[12:05.16]n.散热器 n.灯丝

[12:07.38]Exercises Section I Listening Comprehension

[12:14.04]Listen to the record.

[12:17.99]Answer each question by choosing A,B,C or D from the possible choices.

[12:25.93] 1.I need to get car insurance.You got any ideas?

[12:34.39]Well,you could try my company.It seems to have fair rates.

[12:39.95]Sir.Your bags ar 40 ponds overwight.You are allowed only 25 pounds of baggage.

[12:49.70]Well then,how much do I owe you?

[12:53.46]You're putting on a little weight,aren't you? I know.Don't remind me.

[13:01.22]I'm starting a new diet today.

[13:05.97]Where can I exchange some money?

[13:11.61]You'll have to go to the Bank of China,but it closes at 5:00 p.m.

[13:17.86]I'm a scientist.I've just finished a paper on computer 5.

[13:25.30]Oh? That's my field,too.I work for an institute.

[13:30.76]How exactly do you figure out the car fares?

[13:37.53]Well,the first five kilometres are ten dollars

[13:42.07]and every extra kilometre costs you one dollar.

[13:46.80]The dictionary is $58 and the textbook is $25.

[13:54.87]Here's a hundred dollar bill.

[13:58.53]How long will it take you to repair my computer?

[14:04.70]I'll call you when it's ready,but it shouldn't take longer then two weeks.

[14:10.65]How much time did you have for writing the composition?

[14:16.82]We were given 2 hours,but I finished in less than half the time.

[14:22.98]What do you think of my article? The ideas are good.

[14:29.83]If I were you,I'd rewrite the last two paragraphs to make it better.

[14:36.59]B Everyone seems to be on a diet.

[14:42.16]have you noticed that,Jane?

[14:45.68]Everyone seems to be talking about diets.

[14:50.93]A neighbour of mine is on an orange diet.

[14:55.50]She eats an orange for breakfast,an organge for lunch,and two oranges for dinner.

[15:02.16]That's bad for the health! Has she lost any weight?

[15:07.81]She doesn't look any thinner,but she hasn't been on the diet long.

[15:13.27]A friend of mine eats eggs for breakfast,lunch and dinner.

[15:20.35]He never eats anything but eggs.

[15:25.20]That's bad for the heart!

[15:29.04]Eggs have a lot of protein and protein is good for losing wight.

[15:34.82]To many eggs are bad for the heart.

[15:38.95]I've read that,too.But eggs are cheaper than steak.

[15:45.21]An uncle of mine doesn't eat anything but steak.

[15:50.78]He eats steak for breadkfast.

[15:55.04]The best way to lose weight is to eat less and exercise more.

[16:00.91]C You should be careful with fires.

[16:05.96]People who are not careful cometimes cause fires that burn buildings or forests.

[16:13.90]If youa re ever in building,Crawl on the floor to a door and get out.

[16:20.98]The smoke and heat from the fire are in the upper part of a room.

[16:27.64]The air near the floor is cooler and fresher.

[16:33.10] If your clothing get on fire,

[16:37.46]roll on the ground or wrap yourself in a blanket to shut out the air.

[16:44.41]With no air,the fire will go out.

[16:49.45] Firemen sometimes put out fires by spraying water on them.

[16:55.90]The water cools the burning material so that the fire goes out.

[17:02.25]Supplementary Reading

[17:05.80]Computers and Crime

[17:09.75]No one who reads the newspapers can doubt the seriousness of this country.

[17:16.23]Not a day goes by without numberous robberies,rapes,and murders being reported.

[17:23.59]In amny cities,It's extremely dangerous to walk the street at night.

[17:29.55] Crime is a complex problem with many causes.

[17:35.29]Poverty,unemployment,conditions in the cities,

[17:40.73]and increasing disregard for authority all play their roles

[17:46.76]and no single remedy is going to solve the problem overnight.

[17:52.33] But perhaps at least one of the causes can be dealt with

[17:57.97]-- the inefficiency of the criminal justice system.

[18:03.12]For instance,

[18:06.28]the police usually are able to solve only a fraction of the crimes committed.

[18:13.41]And offenders are apprehended,

[18:17.25]there is usually a long delay in trial and sentencing.

[18:22.50]During the delay,the offenders may be out on bail committing more crimes.

[18:29.73] Much police work concerns information--information about stolen property,

[18:37.28]fugitives from justice,the methods of operation of known criminals.

[18:43.76]The computer can make an important contribution to processing

[18:49.40]this information effectively and efficiently.

[18:54.37] Unfortunately,there is almost no other area in which computers inspire such fear.

[19:02.23]The reason is obvious:

[19:06.20]the police can initiate proceedings that can take a person's liberty away.

[19:12.65]And,sometimes with good reason,

[19:16.91]not everyone is convinced that those proceedings will be carried out fairly.

[19:23.68]Even worse,the police keep records that can haunt us the rest of our lives.

[19:30.91]Even those people who have the most to fear from crime may fear

[19:37.37]even more anything that increase the effectiveness fo the police.

[19:43.14] (The fact taht large segments of the population do distrust the police

[19:49.98]is one more reason there will be no easy solutions to the problem of crime.)

[19:56.75] In one way,the computer can be considered a mixed blessing for law enforcement.

[20:03.91]To be sure,it helps the police solve crimes and apprehend criminals.

[20:10.15]But it also opens up a whole new world of ways to commit crimes.

[20:16.52]As far back as 1974,authorities estimated that over 200 million

[20:24.57]were being lost each year through computer-related crime.

[20:30.03]That figure certainly ahs not diminished in the intervening years.

用手机学英语,请加听力课堂微信公众号:tingclass123
用户搜索

疯狂英语 英语语法 新概念英语 走遍美国 四级听力 英语音标 英语入门 发音 美语 四级 新东方 七年级 赖世雄 zero是什么意思台州市嘉丽名都英语学习交流群

网站推荐

听歌学英语英语学习方法

  • 频道推荐
  • |
  • 全站推荐
  • 广播听力
  • |
  • 推荐下载
  • 网站推荐