04 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 million 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 cell 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, cert 04 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 million 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 cell 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 cell are linked together, the effects can be astonishing.
The electric eel is an amazing storage battery. It can seed a jolt of as much as eight hundred volts of electricity through the water in which it live. As many as four-fifths of all the cells in the electric eels body are specialized for generating electricity, and the strength of the shock it can deliver corresponds roughly to length of its body.
ain muscle cells have become so specialized as electrical generators that they do not work as muscle cells at all. When large numbers of these cell are linked together, the effects can be astonishing.
The electric eel is an amazing storage battery. It can seed a jolt of as much as eight hundred volts of electricity through the water in which it live. As many as four-fifths of all the cells in the electric eels body are specialized for generating electricity, and the strength of the shock it can deliver corresponds roughly to length of its body.
故事还在里面
三国故事:三英战吕布
三国故事:夜战马超
三国故事:黄忠请战
三国故事:马跃檀溪
少儿英语故事视频大全 第1期:白云 Clouds
三国故事:诸葛亮吊孝
三国故事:江东赴会
讲故事
三国故事:计收姜维
少儿英语故事视频大全 第11期:当地上有雪时
三国故事:横槊赋诗
三国故事:蒋干盗书
少儿英语故事视频大全 第13期:荡秋千
格林童话: 小海兔的故事
安徒生童话:母亲的故事
放生的故事:天然的免疫
三国故事:计取陈仓
三国故事:单骑救主
三国故事:水淹七军
伊索寓言《两个年轻人和熊的故事》
三国故事:设连环计
伊索寓言之《农夫和蛇的故事》
三国故事:初出茅庐
少儿英语故事视频大全 第2期:饼
三国故事:刮骨疗毒
放生的故事:长寿、快乐和荣誉
格林童话: 麦穗的故事
三国故事:辕门射戢
三国故事:击鼓骂曹
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |