2. 外语
  3. The Tiniest Electric Motor in the World 1. Scientists recently made public the tiniest electric motor ever built. You could stuf

The Tiniest Electric Motor in the World 1. Scientists recently made public the tiniest electric motor ever built. You could stuf

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问题            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 tiny 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 even 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, grows—but never gets as big as the other droplet—and 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 tension—the 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—20 microwatts—it is quite impressive in relation to the tiny scale of the motor. The whole setup is less than 200 nanometers on 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 100 million times more powerful than a Toyota Camry’s 225 horsepower V6 engine.
5. In 1988 , Professor Richard Muller and colleagues made the first operating micromotor, which was 100 microns across, or about the thickness of a human hair. In 2003, Zettl’s group created the first nanoscale motor. In 2006, they built a nanoconveyor, which moves tiny particles along like cars in a factory.
6. Nanotechnology engineers try to mimic nature, building things atom-by-atom. Among other things, nanomotors could be used in optical circuits to redirect light, a process called optical switching. Futurists envision a day when nanomachines, powered by nanomotors, travel inside your body to find disease and repair damaged cells.
A. An Introduction of a Toyota’s 225 Horsepower V6 Engine
B. A Description of the Nanomotor in Terms of Power and Size
C. Surface Tension
D. Previous Inventions of Nanoscale Products
E. The Working Principle of the Nanomotor
F. Possible Fields of Application in the Future
Paragraph 5______
选项
答案D
解析 本题考查的是对所读材料大意与主旨的掌握。第五段介绍了发明纳米发动机之前的一些纳米等级的机械产品，如体积大一些的纳米发动机、微型发动机、纳米传送带、纳米机器等。选项D概括了本段的大意，所以D是答案。
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