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While we're on the topic of fringing fields:
1) We are all familiar with the notion that the field
inside a long solenoid is uniform. This is mostly true.
2) There is a widespread misconception that the uniform
field extends all the way to the ends, so that the flux
lines shoot straight out the end like water shooting out
of a garden hose. This is not right.
You can easily show (by symmetry!) that the field right
at the end of long solenoid is half the strength of the
field at a typical point not near the end. That means
that half the field lines have "leaked out" sideways
before reaching the end. There's a whole lot of fringing
going on.