Rotor losses, an important form of power losses in induction motors, are largely but not entirely proportional to the square of the slip (slip is the difference between the rotational speed of the magnetic field and the actual rpm of the rotor at a given load). Thus, rotor losses are reduced by decreasing the degree of slip for a given load. This is accomplished by increasing the mass of the rotor conductors (conductor bars and end-plates) and/or increasing their conductivity, and to a lesser extent by increasing the total magnetic field across the air gap between rotor and stator.