ABSTRACT
This chapter first identifies the factors that affect the force acting on a current-carrying conductor lying within a magnetic field. It then states the relationship between the torque developed by a DC motor and its volume. Next, the chapter derives an equation for power developed by a simple loop DC motor, in terms of its torque and rotational speed. It then shows how a de Prony brake can be used to determine the torque, power, and efficiency of a DC motor. The chapter also derives an equation for the torque developed by a practical DC motor, and explains the difference between the armature reaction of a DC motor and a DC generator. It presents schematic diagrams, showing the differences between a shunt, a series, and a compound DC motor. Finally, the chapter sketches the torque characteristic, speed characteristic, and torque/speed characteristic for a shunt, series, and compound DC motor.
