NEIEP Mechanics Practice Exam

What is the primary type of resistance used in a DC motor?

1. Inductive resistance

2. Capacitive resistance

3. Armature resistance

4. Impedance

The correct answer is: Armature resistance

In a DC motor, the primary type of resistance is armature resistance. This is because the armature is the rotating part of the motor, containing coils of wire through which current flows. As electrical current passes through the armature windings, it encounters resistance due to the material of the wire, typically copper. This armature resistance is crucial because it impacts the performance of the motor, affecting the current flow and the amount of heat generated during operation. Armature resistance plays a significant role in determining the voltage drop across the armature when the motor is running. When a load is applied to the motor, the current increases, resulting in a greater voltage drop across the armature resistance. This, in turn, influences the motor's efficiency and overall performance. Other types of resistance, such as inductive and capacitive resistance, are not primarily associated with DC motors. Inductive resistance relates more to inductors and inductive reactance in AC circuits, while capacitive resistance describes the opposition to change in voltage in capacitors. Impedance is a broader term that refers to the total opposition to current flow in an AC circuit, including both resistance and reactance components, but it is not directly applicable to the predominant resistive element in a DC motor