Fig. 1.1 shows a bar magnet placed on a sheet of white paper. Iron filings have been sprinkled around the magnet and the paper has been tapped gently. The m...

(a) A magnetic field is a region in which a magnetic pole experiences a force. [1]

This definition is precise: it describes the field not as the lines themselves but as the space where a pole (or magnetic material) would feel a push or pull.

(b) At point P (to the left of the north pole), the direction of the magnetic field is away from the north pole, pointing to the left. [1]

By convention, magnetic field lines run from north to south outside the magnet. Since P is beyond the north pole, the field at P points outward, away from N (i.e. to the left in the diagram).

(c) The magnetic field is strongest near the poles. [1]

Iron filings cluster where the field is strongest because the force on each filing is greatest there. Closer field lines represent a stronger field, so the filings pack tightly near the poles where lines converge. Further from the poles, the lines spread apart, the field weakens, and the filings are more spaced out. [1]

(d) The procedure to trace one complete field line:

1. Place the plotting compass near the north pole of the magnet. Mark with a pencil dot the position of both the north-pointing tip and the south-pointing tail of the compass needle. [1]
2. Move the compass so that its tail (south-pointing end) sits on the position previously occupied by the tip (north-pointing end). Mark the new position of the tip. [1]
3. Repeat this process, always advancing the compass so the tail sits on the last tip mark. Continue until the trail of dots reaches the south pole of the magnet. Join the dots with a smooth curve and add an arrow pointing from N to S to complete the field line. [1]

Each step advances the compass by one needle-length along the field direction. The resulting curve shows the path a free north pole would follow.

(e) At point R (directly above the magnet, between N and S), the compass needle aligns along the field direction at that point. It points roughly parallel to the magnet, from the N-pole side towards the S-pole side (i.e. along the field line that arcs over the top of the magnet). [1]