解放军文职招聘考试Electricity

 Electricity

The modern age is an age of electricity. People are so used to electric

lights, radio, televisions, and telephones   that it is hard to imagine what

life would be like without them. When there is a power failure, people

grope about in flickering candlelight, cars hesitate in the streets because

there are no traffic lights to guide them, and food spoils in silent

refrigerators.

 

Yet, people began to understand how electricity works only a little more

than two centuries

ago. Nature has apparently been experimenting in this field for millions of

years. Scientists are discovering more and more that    the living world may

hold many interesting secrets of electricity that could benefit humanity.

All living cells send out tiny pulses of electricity. As the heart beats,

it sends out pulses of record;  they form  an electrocardiogram, which  a

doctor can study  to determine  how well the heart is working. The brain,

too, sends    out brain waves of electricity, which can be recorded in an

electroencephalogram.  The electric currents  generated  by most living

cells are  extremely small -- often so small that sensitive instruments are

needed to record them.   But in some animals, certain muscle cells have

become so specialized as electrical generators that they do not work as

muscle cells  at  all. When  large  numbers of  these cells are linked 

together, the  effects can  be astonishing.

The electric eel is an amazing storage battery. It can send a jolt of as

much as eight hundred volts of electricity through  the water in  which  it

 lives. (An electric house current is only one hundred twenty volts.)  As 

many as four-fifths  of all  the  cells in  the electric eel's  body are

specialized for generating electricity, and the  strength of the shock it 

can deliver corresponds roughly to the length of its body.

电  当今时代是电气时代。 人们对电灯、收音机、电视和电话早已司空见惯以致很难想 象没有它们生活会变成什么样。

当停电时，人们在摇曳不定的烛光下暗中摸索； 因没有红 绿灯的指示，汽车在道路上迟疑不前；冰箱也停止工作，导致食物变质。人们只是在两个世

纪前一点才开始了解电的使用原理，自然界却显然在这方面经历过了数百万年。  科学家不

断发现许多生物世界里可能有益于人类的关于电的有趣秘密。所有生物细胞都会发出微小的 电脉冲。 

当心脏跳动时，把它发出的脉冲记录下来就成了心电图，这可让医生了解心脏的 工作状况。大脑也发出脑电波，这可在脑电图上记录下来。 

许多生物细胞发出的电流都是 极微小的，小到要用灵敏仪器才能记录和测量。  但一些动物的某些肌肉细胞能转化成一个 个发电机，以致完全失去肌肉细胞的功能。

 这种细胞大量地连接在一起时产生的效果将是 非常令人吃惊的。电鳗就是一种令人惊异的蓄电池。  它可以在水中发出相当于 800 伏特电

压电流(家庭用户的电压只有  120  伏特)。  在电鳗的身体里，多至五分之四的细胞都专门用 来发电，而且发出的电流的强度大约和它身体的长度成正比。