In a direct current (DC) motor, a split-ring commutator is connected to the rotating coil. Which of the following describes the key function of the split-ring commutator?
It reverses the polarity of the external power supply every half turn.
It reverses the direction of the current in the coil every half turn to ensure the turning effect (torque) remains in the same direction.
It maintains a constant direction of current within the coil throughout its entire rotation.
It reverses the direction of the external magnetic field every half turn.
31 exam-style questions on CIE IGCSE Physics 4.5.5 The d.c. motor. Each one has a worked solution and a mark scheme showing where the marks go.