An alloy bar magnet is placed inside a long solenoid connected to an electrical power supply.
Which method will successfully demagnetise this magnet?
Connect the solenoid to a high-voltage d.c. supply, then switch off the current.
Connect the solenoid to an a.c. supply, then slowly withdraw the magnet a long distance away from the solenoid.
Connect the solenoid to an a.c. supply, then quickly turn off the supply while the magnet is inside.
Connect the solenoid to a d.c. supply, then slowly withdraw the magnet a long distance away from the solenoid.
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.