What is one method to change the direction of rotation in a dc electric motor?

To change the direction of rotation in a DC electric motor, one effective method is to switch the electrical connections to either the field or armature windings. This works because DC motors operate on the interaction between the magnetic field and the current flowing through the windings. By reversing the direction of current flow in either the field winding or the armature winding, the resulting magnetic forces acting on the rotor are also reversed. This reversal changes the direction of torque applied to the rotor, thus altering its rotational direction.

Altering power source voltage, changing the motor type, or reversing mechanical connections do not directly achieve the desired effect of reversing rotation in a straightforward manner. In essence, simply switching the electrical connections is a quick and effective way to achieve the directional change needed in the motor's operation.