Van Allen has experimentally observed that the magnetic moments of the planets and stars are proportional to their angular momentum over some 12 orders of magnitude. "This, graph is purely empirical and is regarded with disdain by theorists of planetary magnetism."-Van Allen. In this paper, I develop a model, that both predicts the proportionality between magnetic moment and angular momentum and also fits the experimental results with no adjustable parameters. The model is based on the fact that each rotating planet and star is immersed in a nonrotating conducting plasma cloud, which constitutes a Faraday electrical generator. This Faraday generator is assumed to be the primary source of the magnetic field, in contrast to present models that assume that the flow of magma in the planets' cores is responsible.