Consider the following statements: Statement I: The magnetic field lines emerge from the north pole and merge at the south pole of a bar magnet. Statement II: The direction of magnetic field is taken to be the direction in which the north pole of a compass needle moves. Statement III: There is no field inside a bar magnet. Statement IV: The relative strength of the magnetic field is shown by the degree of closeness of the field lines. Which of the above statement(s) is/are correct?

Magnetic field lines

• In a magnetic field, magnetic field lines are the lines whose tangent at any point indicates the direction of the field and whose density indicates the field's magnitude. The magnetic field lines emerge from the north pole and merge at the south pole of a bar magnet.
• Hence statement I is correct.
• The number of magnetic field lines determines the intensity of the field.
• The magnetic field is stronger at the poles because the lines are higher there.
• The number of magnetic field lines at a given location determines the strength of a magnetic field.
• Hence statement III is incorrect.
• The direction of magnetic field is taken to be the direction in which the north pole of a compass needle moves.
• Hence statement II is Correct.

Bar Magnet

• A bar magnet is a rectangular piece with permanent magnetic properties made of iron, steel, or another ferromagnetic substance or ferromagnetic composite.
• It has a north pole and a south pole, so when it is free to move, the magnet aligns itself so that the northern pole faces the earth's magnetic north pole.
• The like and unlike poles of two bar magnets will repel one another if they are placed close to one another.
• Hence, Statement IV is correct.
• All ferromagnetic substances, including iron, nickel, and cobalt, will be attracted by a bar magnet.