首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The idea of a fish being able to generate electricity strong enough to light lamp bulbs—or even to run a small electric motor—is
The idea of a fish being able to generate electricity strong enough to light lamp bulbs—or even to run a small electric motor—is
admin
2012-03-04
120
问题
The idea of a fish being able to generate electricity strong enough to light lamp bulbs—or even to run a small electric motor—is almost unbelievable, but several kinds of fish are able to do this. Even more strangely, this curious power has been acquired in different ways by fish belonging to very different families.
Perhaps the best known are electric rays, of which several kinds live in warm seas. They possess on each side of the head, behind the eyes, a large organ consisting of a number of hexagonal shaped cells rather like a honeycomb. The cells are filled with a jelly-like substance, and contain a series of flat electric plates. One side, the negative side, of each plate, is supplied with very fine nerves, connected with a main nerve coming from a special part of the brain. Current passes from the upper, positive side of the organ downwards to the negative, lower side. Generally it is necessary to touch the fish in two places, completing the circuit, in order to receive a shock.
The strength of this shock depends on the size of the fish, but newly born ones only about 5 centimeters across can be made to light the bulb of a pocket flashlight for a few moments, while a fully grown torpedo gives a shock capable of knocking a man down, and, if suitable wires are connected, will operate a small electric motor for several minutes.
Another famous example is the electric eel. This fish gives an even more powerful shock. The system is different from that of the torpedo in that the electric plates run longitudinally and are supplied with nerves from the spinal cord. Consequently, the current passes along the fish from head to tail. The electric organs of these fish are really altered muscles and like all muscles are apt to tire, so they are not able to produce electricity for very long. People in some parts of South America who value the electric eel as food, take advantage of this fact by driving horses into the water against which the fish discharge their electricity. The horses are less affected than a man would be, and when the electric eels have exhausted themselves, they can be caught without danger.
The electric catfish of the Nile and of other African fresh waters has a different system again by which current passes over the whole body from the tail to the head. The shock given by this arrangement is not so strong as the other two, but is none the less unpleasant. The electric catfish is a slow, lazy fish, fond of gloomy places and grows to about 1 meter long; it is eaten by the Arabs in some areas.
The power of producing electricity may serve these fish both for defense and attack. If a large enemy attacks, the shock will drive it away; but it appears that the catfish and the electric eel use their current most often against smaller fish, stunning them so that they can easily be overpowered.
How many kinds of fish which can generate electricity are mentioned in this passage?
选项
答案
Three
解析
转载请注明原文地址:https://kaotiyun.com/show/kNVK777K
本试题收录于:
C类竞赛(非英语专业本科)题库大学生英语竞赛(NECCS)分类
0
C类竞赛(非英语专业本科)
大学生英语竞赛(NECCS)
相关试题推荐
Iamgoingtoworkinatotallynewenvironment.【T1】________.Iamusedtoworkinginquitehigh-techsortofindustrythathas
A、Theenvironmentisbad.B、Thefoodisnotdelicious.C、Thechickenisnotfresh.D、Thechickenisnotcleanenough.D由原文可知,男士担
DoSomethingtoImproveYourLifeWrongopinionstowardslife.wrongopinions—peoplehavetoacceptwhateverlife【
ItooktoherthemomentImether.Theunderlinedpartmeans________.
Nothingbutsomemagazines________inherhandbag.
Ifyouareanathlete,strongabdominalmuscleshelpyouensureastrongbackandfreedomfrominjuryduring________upper-bodym
(1)Theurbanpopulationin2014accountedfor54%ofthetotalglobalpopulation,upfrom34%in1960,andcontinuestogrow.A
毕竟世上有这样一些人,他们渴望和平、安宁的生活。(eagerfor)
教师被人们称为“园丁”、“人类灵魂的工程师”,是受到全社会尊重的一种职业。每年的10月5日为世界教师日。【T1】该节日旨在赞扬和感谢全世界教师为教育事业和人类作出的贡献(contribution)。同时希望引起对教师的世界性关注,帮助教师维护自身权益。
ExactlywhatapublicforestisandhowthepublicshouldbeabletouseithasbeendebatedsincetheNationalForestswerefir
随机试题
支气管动脉栓塞治疗大咯血的适应证包括以下哪项
【案例】患者,女,24岁。因与家人口角于30分钟前口服敌百虫约20mL而入院治疗。体检:嗜睡状,大汗淋漓,呕吐数次,全身皮肤湿冷,无肌肉震颤;双侧瞳孔直径2~3mm,对光反射存在:体温、脉搏、呼吸及血压基本正常;双肺呼吸音粗;化验:WBC14.
申请设立期货公司,应当具备的条件包括( )。
求幂级数的收敛域.
"Thisisareallyexcitingtime,aneweraisstarting,"saysPeterBazalgette,thechiefcreativeofficerofEndemol,thetelev
在窗体上添加一个命令按钮(名为Command1)和一个文本框(名为Text1),并在命令按钮中编写如下事件代码:PrivateSubCommand1_Click()m=2.17n=Len(Str$(m)+Space(
OrderingRoomServiceRoomNo.:【L5】______Whatfordinner:twofreshJuices,oneorangeandone【L6】______,tworoastbeefsandw
Recentresearchfromanimalbehavioristssuggeststhat"asthecrowflies"shouldnolongerbetakentomean"theshortestdista
Whichistrueaboutthespeaker’simplication?
LaughterIstheKeytoHappinessI.Howtobehappier?1)tonsofthingsrelatedtohappiness—【T1】,hobby,agoodjob,awarmf
最新回复
(
0
)