NEIEP Mechanics Practice Exam

What should be done if a motor runs too slow?

1. Increase the load

2. Decrease the field strength

3. Increase the armature voltage

4. Change the commutator type

The correct answer is: Increase the armature voltage

If a motor is running too slow, increasing the armature voltage is a viable solution. This is because the speed of a DC motor is directly related to the voltage applied to the armature. By increasing the armature voltage, you provide more electrical power to the motor, which can result in a higher speed of rotation. In many cases, the armature of a motor acts as the primary driver for its speed, and higher voltage can help overcome any resistive losses that may be causing the slowdown. This adjustment effectively increases the input energy available for the motor to convert into mechanical energy, enhancing its performance. The other choices don’t address the speed directly. Increasing the load, for instance, would likely cause the motor to slow down further as it struggles to handle the additional demand. Decreasing the field strength can also influence the speed, but it often leads to reduced torque as well, which might not be helpful depending on the application. Changing the commutator type is unlikely to resolve speed issues, as it is more about the efficiency and smoothness of operation rather than directly influencing the running speed.