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Re: [Phys-L] amusing electrostatics exercise



On 02/27/2013 02:48 PM, Bernard Cleyet wrote:

I specifically specified: "For simplicity assume infinite length."
To avoid the prob. discussed at length.

I interpreted that to mean that there was a small hole in an
infinitely long wire. As I said, the problem was seriously
underspecified.

The original question specifically said the hole was "non co-axial".
The original question said the hole went "thru" the wire -- not along
the wire. According to the #1 dictionary definition of "through", it
means in one side and out the other.
http://www.thefreedictionary.com/?Word=through
All in all, for multiple good reasons I assumed the hole was transverse
and therefore necessarily short. Evidently several other people assumed
the same thing.

However, no matter what kind of hole we assume
-- transverse or not
-- short or not
it doesn't change the fact that the problem cannot possibly have
a simple solution, for reasons previously explained. The shape
of the wire affects the shape of the field (duh). The shape of the
hole affects the shape of the (remaining) wire (duh). All the
rest is either working out the details ... or deciding to ignore
the details. In any case, the answer depends on as-yet unspecified
parameters of the problem.

This was a prob. in the qualifying exam at UCSC.

It looks to me like an ESP exam. The only way to come up with a
definite answer is to read the mind of the person who posed the
question, in order to divine what was intended.