The principle of a hair dryer is a fan (high speed, large air volume) and an electric heating wire (used to blow hot air)
The wind blown by the fan passes through the electric heating wire and then comes out through the hair dryer. If the electric heating wire If it is not turned on, it will blow cold air. If the heating wire is turned on (there is a switch on the handle), the air from the fan after blowing through the heating wire will be hot, which is good for drying your hair.
The tail of the hair dryer cannot be blocked. The function of the tail is to suck air. Only by keeping the air flowing can there be wind.