Magnets and magnetic field lines

Properties of magnetic field lines:

• Two magnetic field lines never cross each other. Because each point on the magnetic field has only one direction. If the magnetic field lines cross each other at any point it means that point has two direction of magnetic field at that point which is contradiction.

• Magnetic field lines are vector quantity. Outside the magnet they exit form north pole and enter south pole. Inside the magnet they are parallel to each other and travel south pole and north pole.

• Magnetic field lines form closed loop.

• In the region of strong magnetic field, lines are close to each other and in the region of weak magnetic field lines are far from each other. It means if you see rarer magnetic field lines indicate week field strength and denser magnetic field lines indicate strong magnetic fields.

• Like poles repel and opposite poles attract.

How do we decide the north and south pole of magnet?

• Take bar magnet and piece of thread.

• Tie the string at the centre of magnet so that when magnet is hanged freely its horizontally balanced

• Hang the magnet freely, give it time to settle.