2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/157773The Rayleigh monotonicity is a principle from the theory of electrical networks. Its combinatorial interpretation says for each two edges of a graph G, that the presence of one of them in a random spanning tree of G is negatively correlated with the presence of the other edge. In this paper we give a self-contained (inductive) proof of Rayleigh monotonicity for graphs.7 pagesCombinatorics05C05; 05A20text