A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He sprinkles some iron filings uniformly around the bar magnet. Then he taps the board gently and observes that the iron filings arrange themselves in a particular pattern.

a. Why do the iron filings arrange in a pattern?

b. What does the crowding of iron filings at the end of the magnet indicate?

c. What does the lines along which the iron filings align represent?

d. Draw a neat diagram to show the magnetic field lines around a bar magnet.

e. Write any two properties of magnetic field lines.

The bar magnet kept at the centre of board has its magnetic field around it. The iron filings sprinkled on the board experience a force on them due to the magnetic field of bar magnet. So, when the student taps the board the iron filings align themselves according to the magnetic field lines of the bar magnet.
b. The relative strength of magnetic field is shown by the degree of closeness of magnetic field lines. The iron fillings are crowded near the poles of the bar magnet. This shows that the magnetic field due to the magnet is maximum near the poles of the magnet.
c. The force exerted on the iron filings align themselves according to the magnetic field lines of the magnet. Thus, the lines along which the fillings align represent the magnetic field lines.
The properties of magnetic field lines are:

● They are closed curves. They originate from North pole and merge at the South pole outside magnet. Inside the magnet, they direct from South to North pole.

● No two magnetic field lines can cross each other. If they do, it means that there are two directions of the field at that point which is impossible.