NEIEP Mechanics Practice Exam

Which type of resistor is typically used in door operators to control the motor field voltage?

1. Fixed Resistor

2. Wire Wound Adjustable Resistor

3. Carbon Composition Resistor

4. Metal Film Resistor

The correct answer is: Wire Wound Adjustable Resistor

The type of resistor commonly used in door operators to control the motor field voltage is a wire-wound adjustable resistor. This type of resistor is particularly suitable for applications where variable resistance is required, allowing for effective control over the motor's performance. The wire-wound construction provides high precision and durability, making it capable of handling the power and heat generated in motor applications. In the context of door operators, adjusting the resistance not only affects the voltage and current flowing to the motor but also helps in fine-tuning motor speed and torque, which is crucial for safe and efficient operation. Other types of resistors, such as fixed resistors, lack the adjustability necessary for this level of control, while carbon composition and metal film resistors may not handle the power load as effectively as wire-wound resistors. Hence, the flexibility and robustness of the wire-wound adjustable resistor make it the preferred choice in this application.