🔍 Key Concepts

• Brush pressure is a mechanical force applied to the brushes on a commutator, not an electrical quantity. • Think about instruments that measure mechanical force or weight versus those that measure electrical or fluid pressure. • DC motor maintenance often uses simple mechanical tools to check spring tension or contact pressure.

💭 Think About

• Which of these devices is designed to directly measure a pulling or pushing force in pounds or newtons? • Which devices in the list are mainly used for electrical measurements or fluid pressure measurements, and therefore would NOT be suitable for checking how hard a brush is pressed? • When a technician adjusts brush pressure, what kind of handheld tool could they hook to the brush holder or spring to see how much force it applies?

✅ Before You Answer

• Eliminate any device that measures voltage, current, or resistance—those do not measure mechanical pressure. • Eliminate any device that is normally connected to gases or liquids to read their pressure on a dial. • Select the device that can measure mechanical force/tension applied by the brush spring against the commutator.