Suppose there is an infinite network of one ohm resistors on a square grid.
It is relatively easy to determine the resistance across a side of a square (across one resistor in the network).
How do you determine the resistance between two nodes on a small square diagonal?
How do you determine the restance between a node and the second node over in a straight line?
How do you determine the resistance between two nodes arranged as in a chess knight move? That is one nod and another node that is two steps in one direction and one step at a right angle.
Bill