A delicate, antique steel pocket watch has accidentally become magnetized, causing its mechanical gears to stick. To restore the watch's function without damaging its intricate and heat-sensitive parts, it must be demagnetized.
Which of the following is the most suitable method to demagnetize the watch?
Heat the watch until it glows red hot, then let it cool slowly.
Place the watch inside a solenoid connected to a direct current (d.c.) supply and switch it off.
Place the watch inside a solenoid connected to an alternating current (a.c.) supply and then slowly withdraw it.
Store the watch in a vacuum-sealed bag inside a freezer at −20∘C-20^\circ\text{C}−20∘C for 24 hours.
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.