What is the operating principle of a variable area flow meter, such as a rotameter?

Correct Answer: Option D — The float or rotor is more dense than the fluid being measured and is positioned so that the gravitational force down is balanced by the upward motion of the fluid flow.

Under USCG National Maritime Center examination standards, the accepted correct answer is: The float or rotor is more dense than the fluid being measured and is positioned so that the gravitational force down is balanced by the upward motion of the fluid flow..