What is an essential step in reversing a DC motor?

Swapping the field or armature leads is an essential step in reversing a DC motor because it changes the direction of the magnetic field or the current flow, respectively. In a DC motor, the direction of the motor's rotation is determined by the orientation of the magnetic fields produced by the armature (rotor) and field winding (stator). By reversing either the armature or field leads, you effectively reverse the polarity of the magnetic field, which causes the motor to rotate in the opposite direction. This is a standard practice in DC motor control and is crucial for applications where the direction of operation needs to be changed effectively and efficiently.

Other methods such as reducing voltage or increasing input current may adjust the motor's performance or speed but do not directly change its rotational direction. Disconnecting the power supply stops the motor entirely, which is not a method for reversing its direction.