THE FIELDS OF MOVING CHARGES — Edward Purcell & David Morin
Physics — E&M · tetrahedron-resistance
Problem
Tetrahedron resistance **
A tetrahedron has equal resistors R along each of its six edges. Find the equivalent resistance between any two vertices. Do this by:
(a) using the symmetry of the tetrahedron to reduce it to an equivalent resistor;
(b) laying the tetrahedron flat on a table, hooking up a battery with an emf E to two vertices, and writing down the four loop equations. It's easy enough to solve this system of equations by hand, but it's even easier if you use a computer.