1.- how a compass needle moves when it is placed in a magnetic field????2.- why only certain materials are magnetic?3.-how heating a bar magnet would change its magnetic fiel?PLEASEE
The compass needle is rotated so that it becomes parallel with the magnetic field of Earth. This happens because of the magnetic moment of the magnet's atoms, and this way magnet reaches the lowest energy level. The materials have magnetic properties which are determined by the magnetic moment of their atoms, that depends on the atomic mass and hence the shape of the atom. If you imagine (a very simplified model) that each atom contains electrons spinning around the nucleus and around themselves, they form microscopic electric currents microscopic magnetic fields (Electrodynamics explain how is produced a magnetic field from a non-stable current). The field produced by each electron adds up, as each atom's field has the same direction, and we have a magnetic material. The atoms in a magnet have fixed positions, that are determined by the lowest internal energy of the material. If the magnet is heated, it's atoms gain extra energy and start moving faster and more freely. In this way the initial structure is destroyed, and when the material is cooled again its magnetic field can be found different or completely destroyed.
