If you block the air-inlet for a hair-dryer, the tone of the motor of that hair-dryer seems to rise ...

physics/hair.dryer New

New entry, edited from material collected for the archive and not yet in a released version.

Problem

If you block the air-inlet for a hair-dryer, the tone of the motor of
that hair-dryer seems to rise ... how come?

Show solution

The blower does in fact speed up.  It's because when the inlet is
blocked, the air in the chamber is free to spin faster and faster,
placing little drag on the blower.  With the inlet open, the blower is
constantly sucking in air that ISN'T up to speed, which causes a
constant drag.

-- Chris Best <cab@col.hp.com>