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Re: let's outgrow puzzles



I think problems such as the resistor cube (and the ladder of impedances,
the polyhedron of resistors, the infinite square lattice of resistors,
the monkey and the banana, ...) are very useful as examples, or puzzles
to be solved at leisure. They require and deserve the sort of contemplative
attention I do not associate with the fifty minute examination format.
The resistor cube is an excellent example of the exploitation of symmetry.
However, I maintain that on an examination it will be solved by most good
students who have seen it before, and it will not be solved by most good
students who haven't. That's not what I'm looking for when I give a test.
Rote memory is not to be rewarded.

Yes, Herb; you got it right. My next problem for you is to consider the
infinite square array of resistors each having resistance R. What is the
resistance between junctions across a square diagonal?

Hint: This problem might not be solved on an examination, but it might
yield to work done while in transcendental meditation.

Leigh