Working: The hot-wire anemometer is a fine resistance wire heated by a current passing through it. If a cooler fluid flows past the wire, heat is removed from it by the fluid. The rate of heat transfer varies with the type of fluid, but it also tends to vary as the square root of velocity at which the fluid flows past the wire. If the current in the wire is kept constant, the change in resistance due to the cooling will yield a voltage signal. It is very sensitive and responsive to high-frequency change in flow rate. One of its main application is aerodynamic research.