Process of demagnetisation can be achieved by:
- placing magnet in east west direction
- hitting or heating the magnet.
→ placing magnet in east west direction minimises influence of earths magnetic field during the demagnetisation process.
- dropping magnet multiple times on a hard surface → can also cause magnet to lose magnetism
Also possible to demagnetise magnet → using solenoid with ALTERNATING CURRENT
- alternating current is one that changes direction all the time
magnetic field of solenoid → produced by alternating current → will change direction every time the current changes direction.
To demagnetise magnetised object (or perm magnet) using solenoid, we have to:
- place magnet inside the solenoid in the east west direction and
- then gradually reduce current to 0
Alternatively → instead of reducing current to 0 → we ca also pull object out of the solenoid until it is some distance away.
| 1. Apply an alternating current to the magnet that is placed inside a solenoid in the east west direction |  | 2. with the alternating current still flowing, pull the magnet out of the solenoid slowly until it is far enough from the solenoid. |
When subjected to long periods of heat or influence from nearby magnetic fields → magnets can become demagnetised.
- to prevent this from happening → we make use of iron keepers → magnetic field is retained within the iron keepers to preserve its strength.
Keepers also have safety function
- they reduce stray magnetic fields of stored magnets and prevent unwanted magnetised materials from being attracted to the stored magnets.
Magnet loses its magnetism → when the atomic magnets are no longer aligned
- this out of alignment → happens when magnets are subjected to heating or dropping repeatedly.
- heating / dropping → causes atomic magnets to vibrate and settle in their preferred orientation
Magnetism does not get used up → like charges in battery Magnetism also does not get transfered when attracted to non-magnetic substances or when placed in contact with another magnet (in case of induced magnetism) → However magnetism does leak over time. → magnet subjected to the influence of external magnetic field and temperature variations → may lose its magnetism gradually.