Which statement about DC motor components is true?

• A. Magnets are not used in DC motors
• B. The commutator is always stationary
• C. Brushes are a typical part of a DC motor
• D. Wood insulating blocks are standard in all designs

Answer: (C)

Brushed electrical contact to the rotating winding is a defining feature of many DC motors. In a typical brushed DC motor, magnets create the static magnetic field while windings on the rotor carry current to generate torque. The current is supplied to those rotating windings via a split-ring commutator that reverses the winding’s current every half turn to keep the torque in the same direction. Brushes, usually carbon blocks, press against the commutator to provide this electrical connection as the rotor turns. That combination—brushes plus a commutator—is what makes a motor a brushed DC motor, and brushes are indeed a typical part of many such motors.

Magnets are used to create the field, so saying magnets aren’t used isn’t correct. The commutator actually rotates with the rotor, so it isn’t stationary. Wood insulating blocks aren’t standard in motor designs; materials chosen for insulation are suitable for electrical and thermal requirements, not typically wood.