The noise produced by a ___________ cooled machine is less as the rotor moves in a medium of smaller density?
Correct answer: B. hydrogen
- A. air
- B. hydrogen
- C. either A. or B.
- D. none of the above
Explanation
Hydrogen is much less dense than air, so a rotor experiences less windage and produces less aerodynamic noise while rotating in it. Air-cooled machines therefore tend to be noisier at the same speed.
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