The polarity of the voltage applied to the electromagnetic coils of a working DC motor is controlled by what component?

The component that controls the polarity of the voltage applied to the electromagnetic coils of a working DC motor is the commutator. In a DC motor, the commutator serves as a switch that reverses the current direction through the motor's windings as the rotor turns. This is crucial because it ensures that the magnetic field produced by the windings maintains a consistent interaction with the stator's magnetic field, allowing the rotor to keep turning in the same direction.

As the rotor spins, the commutator periodically changes the connection of the coil windings to the power supply, effectively flipping the voltage polarity and enabling continuous rotation. This design is fundamental in DC motors, as it allows for smooth operation without interruptions in motion.

The other components mentioned serve different functions: transistors can control the flow of current but do not change its polarity directly; capacitors are used for storing electrical energy and filtering interference; and resistors limit current flow. Hence, their roles do not involve managing the polarity as effectively as the commutator does in a DC motor's operation.