A simple direct-current (DC) motor consists of a coil of wire suspended in a magnetic field.
Which change would result in a decrease in the turning effect (torque) on the coil?
Decrease the potential difference of the power supply.
Increase the number of turns of wire on the coil.
Replace the permanent magnets with stronger ones.
Insert a soft iron core into the center of the coil.
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.