A coil of wire is suspended between the poles of a magnet. The coil consists of 30 turns of insulated wire and is connected in series with a variable resistor and a DC power supply.
Which of the following modifications would result in a decrease in the turning effect on the coil?
replacing the permanent magnet with a weaker magnet
decreasing the resistance of the variable resistor
increasing the number of turns in the coil to 50
increasing the voltage of the power supply
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.