For a universal motor, what is a key characteristic?

A key characteristic of a universal motor is its ability to run on both AC and DC voltage. This versatility arises from its design, which includes a stator and rotor that can function effectively regardless of the type of current being supplied. In a universal motor, the winding configurations and the commutator allow the motor to switch seamlessly between alternating and direct current. This capability makes it particularly useful in various applications, including power tools and household appliances, which often operate on AC power but may also utilize DC sources.

The other choices highlight aspects that do not apply universally to all universal motors. While some types of motors may be limited to single-phase power or specific applications, the defining feature of a universal motor is its dual-voltage capability. Furthermore, universal motors do require a commutator as part of their functioning mechanism; this is essential for reversing the direction of current in the armature as it rotates, thereby maintaining torque in the desired direction. The assertion regarding the usage primarily in industrial applications does not reflect the wider use of these motors in consumer goods as well. Therefore, the ability to operate on both AC and DC is what distinctly characterizes a universal motor.