This paper deals in a general manner with the electromagnetic forces exerted between current-carrying conductors. The factors introduced by the use of alternating current are taken into account and the effects upon the forces of conductor shape, current distribution, and proximity of inductive material, are considered. The characteristics of the forces, the reactions they produce, and the effects of resonance, are also examined.The results of the investigation are given either in general terms or in the form of equations, which are presented in a manner convenient for use in the calculation of electromagnetic forces on alternating-current circuits.