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TOEFL Directory > TOEFL writing > 04 Electricity
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. ( 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 length of its body.
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