Continuous duty rotary solenoids convert axial motion into rotary stroke and are rated for 100% duty cycle. They typically remain in an on-state without interruptions for periods of approximately 30 minutes or longer. Like other types of solenoids, these devices convert electrical energy into mechanical power. Many continuous duty rotary solenoids consist of a plunger and small ball bearings that ride on an inclined plane. Electrical current is supplied to a coil that is wound tightly enough to limit the current drain and sized large enough to provide for adequate heat dissipation. The resulting magnetic field draws the plunger from its unpowered, extended position to a seated position against a backstop or pole piece. Because the linear force on the plunger is nonlinear with position, the force is relatively high immediately adjacent to the seated position and declines rapidly with increased distance from the seated position. Continuous duty rotary solenoids are considerably larger than intermittent duty devices and provide more pull-and-hold strength. For rotary solenoids that are capable of both intermittent and continuous duty, force ratings vary widely by duty cycle.