A straight wire carrying an electric current is placed in a uniform magnetic field and experiences a magnetic force.
Which of the following changes will result in reversing the direction of this magnetic force?
Reverse the direction of the current, and double the strength of the magnetic field.
Reverse both the direction of the magnetic field and the direction of the current.
Double both the current and the magnetic field strength, keeping their directions unchanged.
Decrease the strength of the magnetic field, keeping all directions unchanged.
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.