A DC drive controls the ___ of a DC motor by varying the current applied to the armature.

A DC drive is designed to manage the operation of a DC motor by controlling the current flowing to the motor's armature. When the current is varied, it directly affects the magnetic field and the interaction of the armature's magnetic field with the stator. This adjustment primarily influences the torque produced by the motor. Torque is the rotational force that allows the motor to perform work, and the ability to change this torque enables the drive to control the motor's performance effectively.

In contrast, while the rotational speed of a DC motor can be affected by the torque, it is not controlled directly by the current to the armature; rather, speed control usually involves additional considerations such as back EMF and the design of the drive system. Voltage is another factor that can influence motor behavior, but in the context of a DC drive, the manipulation of armature current is specifically about torque management. Acceleration, similarly, arises from changes in torque but is not directly regulated by the current in the same isolated way. Thus, the correct emphasis is on how the current affects the torque of the motor, defining the drive's primary function in this context.