[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.
