A current in a solenoid produces a uniform magnetic field inside the solenoid. The magnetic field direction is due south.
Which changes will produce a weaker magnetic field with a direction due north?
Use a smaller current and turn the solenoid through 90∘90^\circ90∘.
Use a larger current and turn the solenoid through 180∘180^\circ180∘.
Use a smaller current and reverse the current.
Use a larger current and reverse the current.
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.