A steel magnet is inserted into a coil of wire. Which technique is used to demagnetise the magnet?
- Aconnect the coil to an a.c. power supply
- Bconnect the coil to an a.c. power supply and slowly remove the magnet from the coil
- Cconnect the coil to a d.c. power supply
- Dconnect the coil to a d.c. power supply and slowly remove the magnet from the coil