• Take a small compass and a bar magnet.

• Place the magnet on a sheet of white paper fixed on a drawing board, using some adhesive material.

• Mark the boundary of the magnet.

• The south pole of the needle points towards the north pole of the magnet.

The north pole of the compass is directed away from the north pole of the magnet.

• Mark the position of two ends of the needle.

• Now move the needle to a new position such that its south pole occupies the position previously occupied by its north pole.

• In this way, proceed step by step until you reach the south pole of the magnet.

• Join the points marked on the paper by a smooth curve. This curve represents a field line.

• These lines represent the magnetic field around the magnet. These are known as magnetic field lines.

• Observe the deflection of the compass needle as you move it along the field line. The deflection increases as the needle is moved towards the pole.