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The first practical direct-current electric motor was invented by

  • A.George Stephenson
  • B.Frank Julian Sprague
  • C.Percy Spencer
  • D.None of these

Answer: B

Frank Julian Sprague built it.

His constant-speed DC motor of 1886 held its speed under varying load, which earlier motors could not, and made electric traction practical. He equipped the Richmond streetcar system in 1888, the first successful electric tramway.

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