This is a page of supplementary information. There are a few for every section.
They are digressions away from the main subject of the Virtual Workshop, and not
a required part. But we think you will find them interesting.
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. It is
one of the few parts 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 buildings have disturbed a little breeze that was blowing,
and the air that was planning on going through the buildings has to
go between them. To move the same amount of air through the smaller gaps
between the buildings, it has to go faster. Hold on to your hat, and
watch out for your umbrella!