A simple dc motor/generator consists of a rotor & a stator. The stator of the machine does not move & normally is the outer frame of the machine; the rotor is free to move & normally is the inner part of the machine. Both of them are usually made up of ferromagnetic materials. Slots are cut on the inner periphery of the stator & the outer periphery of the rotor. Conductors are placed in these slots of the stator or rotor. These are interconnected to form round windings. The winding in which voltage is induced is called armature windings & which current is passed field winding. Permanent magnets are used in some machines to provide the main flux of the machine.