Redistributing magnetic flux density within electro-magnetic or permanent magnet devices, as described herein, causes the device to increase its utilization of its magnetic core material and thereby increase its power density (Watts/volume). The preferred embodiment uses magnetic core bias currents, synchronized to the device's magnetizing current, through uniform, longitudinally isolated, magnetic core sections. The preferred embodiment can be complemented with local core bias currents that generate magnetic flux that oppose the incident magnetizing flux in local magnetic core sections with high flux density concentrations such as core corners. An alternative embodiment longitudinally interlaces magnetically isolated core sections of equal magnetic path length and uniform areal cross section. Another alternative embodiment redirects the magnetic flux in spiral wound inductors and transformers to the circumferential direction used in toroids. All magnetic core shapes, materials, and sizes can be modified to accommodate bias currents; however, the tape wound toroidal core featured mostly in transformers and inductors, is the easiest core to modify. Examples of the types of electro-magnetic and permanent magnet devices that benefit from the appropriate application of magnetic flux density redistribution include electrical devices such as transformers, inductors, delay lines, and electromechanical devices such as motors, generators, relays, solenoids, and rail guns.