Which of the following describes a correct and highly effective method for demagnetising a strong steel bar magnet?
Place the magnet inside a solenoid connected to a large alternating current (a.c.) supply, and slowly withdraw the magnet to a distance far from the solenoid.
Place the magnet inside a solenoid carrying a large direct current (d.c.), then switch off the current suddenly.
Hammer the magnet repeatedly while holding it aligned in a North-South orientation.
Heat the magnet slightly in a water bath to a temperature of about 50∘C50^\circ\text{C}50∘C and then cool it down rapidly in cold water.
169 exam-style questions on CIE IGCSE Physics Simple phenomena of magnetism, covering Simple phenomena of magnetism. Each one has a worked solution and a mark scheme showing where the marks go.