NEIEP Mechanics Practice Exam

What is the recommended material for seating brushes in a generator or motor?

1. Emery cloth

2. Sandpaper

3. Steel wool

4. Paper towel

The correct answer is: Sandpaper

The recommended material for seating brushes in a generator or motor is sandpaper. Sandpaper is designed to provide a controlled abrasive surface that effectively shapes and smooths the contact surfaces of carbon brushes and commutators. When creating a proper seat for the brushes, it is important to establish a good fit that allows for efficient electrical contact without causing excessive wear or damage to the components. Using sandpaper allows for precision in dressing down the surfaces, as it can be easily selected in various grits depending on the desired roughness of the surface. This level of control helps ensure that the brushes make good contact, which is crucial for the performance and longevity of the motor or generator. In contrast, emery cloth, while also abrasive, tends to be more aggressive and may not provide the finer finish needed for brush seating. Steel wool could leave behind fibers or particles that may interfere with the operation of the brushes, and a paper towel does not have any abrasive properties to effectively seat brushes. Hence, the use of sandpaper is the most appropriate choice for this particular application.