NEIEP Mechanics Practice Exam

What type of motor can operate on both AC and DC power?

1. Induction Motor

2. Universal Motor

3. Stepper Motor

4. Servo Motor

The correct answer is: Universal Motor

The universal motor is designed to operate on both alternating current (AC) and direct current (DC) power. This versatility is achieved because of its construction, which typically includes series field windings that enable it to produce high starting torque and maintain speed across a range of voltages. When supplied with direct current, the universal motor functions similarly to a series-wound DC motor, where the armature and field windings work together to create a magnetic field that drives the rotor. When supplied with alternating current, the motor's design allows it to continue functioning effectively, as the windings can handle the changing current direction due to their series configuration. This characteristic makes the universal motor widely used in appliances such as vacuum cleaners and power tools, where high speed and efficiency are necessary. While other types of motors, such as induction motors, stepper motors, and servo motors, are typically designed to operate with a specific type of power source—either AC or DC—the universal motor's compatibility with both types of electricity highlights its unique and practical applications in various settings.