陳蕙雅思教材 - 雅思閱讀精選 (Electricity)

Electricity

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

lights, radio,televisions, and telephones that it ishard to imagine what

life would be likewithout them. When there is a power failure, people

grope about   in flickering candlelight, cars hesitate inthe streets because

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

refrigerators.

Yet, people began tounderstand how electricity works only a little more

than two centuries

ago. Nature has       apparently been experimenting in thisfield for millions of

years. Scientists arediscovering more and more that    the livingworld may

hold many interestingsecrets of electricity that could benefit humanity.

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

it sends out pulses ofrecord;  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 canbe recorded in an

electroencephalogram.  The electric currents  generated      bymost living

cells are  extremely small -- often so small that sensitiveinstruments are

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

become so specialized aselectrical 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 anamazing storage battery. It can send a jolt of as

much as eight hundredvolts of electricity through  the waterin  which it

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

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

specialized forgenerating electricity, and the      strengthof the shock it  

can deliver correspondsroughly to the length of its body.

電  當今時代是電氣時代。 人們對電燈、收音機、電視和電話早已司空見慣以致很難想 象沒有它們生活會變成什麼樣。

當停電時，人們在搖曳不定的燭光下暗中摸索； 因沒有紅 綠燈的指示，汽車在道路上遲疑不前；冰箱也停止工作，導致食物變質。人們只是在兩個世

紀前一點才開始瞭解電的使用原理，自然界卻顯然在這方面經歷過了數百萬年。  科學家不

斷發現許多生物世界裡可能有益於人類的關於電的有趣秘密。所有生物細胞都會發出微小的 電脈衝。  

當心臟跳動時，把它發出的脈衝記錄下來就成了心電圖，這可讓醫生瞭解心臟的 工作狀況。大腦也發出腦電波，這可在腦電圖上記錄下來。  

許多生物細胞發出的電流都是 極微小的，小到要用靈敏儀器才能記錄和測量。  但一些動物的某些肌肉細胞能轉化成一個 個發電機，以致完全失去肌肉細胞的功能。

這種細胞大量地連接在一起時產生的效果將是 非常令人吃驚的。電鰻就是一種令人驚異的蓄電池。  它可以在水中發出相當於 800 伏特電

壓電流(家庭使用者的電壓只有  120  伏特)。  在電鰻的身體裡，多至五分之四的細胞都專門用 來發電，而且發出的電流的強度大約和它身體的長度成正比。