Within the context of this Virtual Workshop on Electricity and Magnetism,
we study fluid flow because electricity is also a kind of fluid -- one which
we cannot see flowing through wires. Study of fluids that we can see makes
the ideas more concrete.
Fluids are interesting for themselves, too. The branch of knowledge that
studies them is called fluid dynamics, and it has the honor of being the only
part of physics that deals with everyday matters for which the mathematical
description is incomplete or at least poorly understood. It is an important
part of the physics
of the weather, and explains how airplanes fly, why a spinning ball curves,
and how the molten interior of the earth gives rise to volcanoes.
Discussing all these would be fun, but we would never get to
electricity and magnetism!
Here are some applications of the ideas of this section:
In a house with forced-air heating or central airconditioning, the
treated air is carried to the various rooms of the house through large ducts.
You might think it is easy to move air, and yet look how large the ducts are!
You complain about not having enough closets, and here all this volume is
dedicated to moving air! But this is a matter of flow rate; smaller ducts
would require higher pressure to make the air move at higher speed -- it
would be noisy and there would be a typhoon at the air registers.
Have you ever noticed that near tall buildings it is unusually
windy? The building has disturbed a little breeze that was blowing,
and the air that was planning on going through the building has
to go around it. This means the flow rate in the regions beside
the building has to be greater, which implies a faster speed.