Mechanical force between electric circuits

A general equation is developed for the mechanical force exerted by a system of n electric circuits, upon any part of that system. The electric circuits are assumed to contain resistances, and the reluctance of the several magnetic circuits is assumed to be a function of both the currents and the relative positions of the circuits. The equation is therefore applicable to circuits involving saturated iron. Special cases of a single circuit and of n circuits are treated, in which a method of graphical solution is given. Also an approximation is made, which results in fairly simple analytical expressions for the force in the case of circuits involving saturated iron. The results are preliminary to an investigation of the forces existing in synchronous machines under the condition of short circuit, which subject will be treated in a forthcoming paper.