Question

Hot wire anemometer is used to measure:

• A. Pressure in gases
• B. Liquid discharges
• C. Gas velocities
• D. Wind velocities

Hint:

Hot wire anemometers work on the principle of \textbf{convective heat loss} and are best suited for measuring \textbf{gas or air velocity} in controlled setups like ducts or laboratories.

Answer 1

The Correct Option is C

A hot wire anemometer is a precision instrument used to measure the velocity of gases, particularly in studies involving turbulence or rapidly fluctuating flows.
It operates based on the principle that the heat loss from a heated wire is proportional to the velocity of the fluid (in this case, gas) flowing past it.
- The wire is electrically heated and placed in the gas stream.
- As the gas flows over the wire, it cools the wire depending on the flow rate.
- The change in temperature (and thus resistance) of the wire is measured, which is directly related to the velocity of the gas.
Important distinction:
- It is especially suitable for measuring small-scale, rapid fluctuations in gas velocity.
- Although sometimes used in wind tunnel testing, it is not typically used for wind velocity in open environments, nor for liquids or pressure measurements.
Thus, the correct application is to measure gas velocities.