A teacher is trying to demagnetise a bar magnet and tests three different procedures. 1. Heat the bar magnet to a high temperature and allow it to cool. 2. Position the bar magnet east to west and strike it with a hammer. 3. Put the bar magnet inside a coil carrying a direct current and withdraw it slowly from the coil. Which methods demagnetise the bar magnet?
- A1 only
- B1 and 2 only
- C2 and 3 only
- D1, 2 and 3