A delicate and precise steel mechanical stopwatch has accidentally become magnetised, causing it to run inaccurately.
Which of the following describes the best method to demagnetise the stopwatch without damaging its delicate internal mechanism?
Heat the stopwatch over a Bunsen burner until it glows red hot.
Connect the stopwatch directly to the terminals of a high-voltage direct current (DC) power supply.
Place the stopwatch inside a coil connected to an alternating current (AC) supply, then slowly withdraw it from the coil.
Seal the stopwatch in a waterproof pouch and submerge it in boiling water for several 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.