A simple DC motor consists of a rectangular current-carrying coil suspended in a magnetic field between two permanent magnetic poles.
Which of the following modifications will increase the turning effect (torque) acting on the coil?
Using a stronger permanent magnet to increase the magnetic field strength.
Adding a resistor in series with the power supply to decrease the current.
Reducing the number of turns in the coil.
Decreasing the cross-sectional area 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.