In order to obtain magnetic field lines around a bar magnet, a student performed an experiment using a magnetic compass and a bar magnet. The magnet was placed on a sheet of white paper fixed on a drawing board. Using magnetic needle he obtained on the paper a pattern of magnetic field lines around the bar magnet.

(a) By convention, the field lines emerge from north pole and merge at south pole. Why? Give reason.

(b) State the relationship between strength of the magnetic field and the degree of closeness of the field lines.

(c) (A) (i) No two field lines can ever intersect each other. Give reason. (ii) The magnetic field in a given region is uniform. Draw a diagram to represent it.

OR

(c) (B) Draw the pattern of the magnetic field lines through and around a current carrying solenoid. What does the pattern of field lines inside the solenoid represent?

Quick Oral Answer

The magnetic field lines emerge from the north pole and merge at the south pole because the magnetic field is created by the alignment of magnetic dipoles in the magnet. The magnetic field lines represent the direction of the magnetic force on a moving charge. The strength of the magnetic field is directly proportional to the degree of closeness of the field lines. The closer the field lines, the stronger the magnetic field. No two field lines can ever intersect each other because the direction of the magnetic field at any point is unique. If two field lines were to intersect, it would mean that there are two different directions of the magnetic field at that point, which is not possible. The pattern of field lines inside a solenoid represents a uniform magnetic field. The field lines are parallel to each other and are evenly spaced, indicating that the magnetic field is uniform throughout the solenoid.