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职称英语理工类考试考前每日一练 The Tiniest Electric.Motor in the World 1.Scientists recently made public the tiniest electric motor ever built.You could stuff hundreds of them into the period at the end of this sentence.one day a similar engine might，power a tmy mechanical doctor that，would travel through your body to remove your disease. 2.The motor works by shuffling atoms between two molten metal droplets in a carbon nanotube.One droplet is eyen smaller than the other.When a small electric current is applied to the droplets，atoms slowly get out of the。larger droplet and join the smaller one.The small droplet growsbut never gets as big as the other dropletand eventually bumps into the large droplet.As they touch，the large droplet rapidly sops up the atoms it had previously lost.This quick shift in energy produces a power stroke. 3.The technique exploits the fact that surface tensionthe tendency of atoms or molecules to resist separating-becomes more important at small scales.Surface tension is the same thing that allows some insects to walk on water. 4.Although the amount of energy produced is small一20 microwattsit is quite impressive in relation to the tiny scale of the motor.The whole setup is less than 200 nanometers off a side，or hundreds of times smaller than the width of a human hair.If it could be scaled up to the size of an automobile engine，it would be l00 million times more powerful than a Toyota Camrys 225 horsepower V6 engine. | 
