Acyclic motors or generators, i.e. DC machines having drum or disc armatures with continuous current collectors with at least one liquid-contact collector. transverse diagrammatic view of a portion of a homopolar generator rotor and its stator shown partly in elevation and partly in section; and a diagrammatic cross sectional view taken through and looking axially of the rotor. This invention relates generally to homopolar (unipolar) electric machinery and more specifically, to means for increasing the power capacity and efiiciency of homopolar generators. The invention described herein was made in the course of, or under, a contract with the US. Atomic Energy Commission. For clarity of description in presenting this invention and since homopolar generators are presently in wider use than homopolar motors, the principles of operation of this invention will be described in terms of the application of the invention in the improvement of the design of homopolar generators. It is, therefore, an object of this invention to provide a means of reducing the aforementioned problems in the design and operation of homopolar generators. It is an object of this invention to provide a more efficient type of homopolar generator rotor having at load conditions a lower internal voltage drop and lower excitation power requirements than the first type, and having lower excitation power requirements at load and no-load conditions than the second type. A homopolar generator in its simplest form comprises a cylindrical rotor of iron or steel rotatable about its longitudinal axis and a stator containing a main pole disposed about the active part of the rotor. Excitation windings located in the stator produce a magnetic flux. The lines of the magnetic flux are directed radially into the rotor by the main pole. The novelty of the device herein disclosed consists in the imbedding of a plurality of nonmagnetic metal rings (such as copper or aluminum) into the periphery of the rotor under the main pole face and beyond (herein defined as the active portion of the rotor). These rings are placed so that each define a plane that is normal to the axis of the rotor. (The rings may not be exactly in this normal plane due to structural design and manufacturing considerations.) Therefore, near the cylindrical periphery of the rotor, a high magnetic reluctance exists longitudinally of the rotor while no additional impedance to the flow of an electric current is presented. Thus, the induction flux from the main pole is forced to remain in a radial direction as it penetrates the periphery of the rotor so as to provide maximum induction. When the circuit is completed across the generator terminals, an electric current resulting from the induced flows longitudinally of the rotor and may be drawn therefrom in the usual manner.