A solid bar is inside a copper solenoid. The solenoid is connected in series with a battery and a variable resistor to form an electromagnet.
Suggest a suitable material for the bar so that it behaves as a temporary magnet.
The right-hand end of the bar is the N pole.
Describe the pattern and the direction of the magnetic field lines outside the bar.
The right-hand end of the bar is the N pole.
The resistance of the variable resistor is decreased. Explain what happens to the current in the solenoid, the strength of the magnetic field surrounding the bar, and how the density of the field lines changes to represent this.
A secondary circular coil of many turns is placed close to the bar, with the plane of the coil parallel to the flat circular surface at the right-hand end of the bar. The resistance of the variable resistor is alternately increased and decreased. Explain what happens in the secondary coil.
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.