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Magnetic Field

  • Substances that are magnetic have a north-seeking pole and south-seeking pole, corresponding to the earth’s magnetic poles. In effect, each magnet has a magnetic field around it just as the earth does.
  • The magnetic field is strongest at the ends of the magnet. In the centre of the magnet the strength is negligible. A magnetic field can be seen by placing a magnet under a piece of paper and then sprinkling iron filings onto the paper. The iron filings line up to show the magnetic field and its concentration, as shown in Fig. 1 (a). 

Fig. 1 (a) Illustrating a magnetic field by the use of iron fillings.

Fig. 1 (b)

  • The unlike poles of two magnets attract each other while the like poles repel each other (Fig. 2).

The following points are worth noting about magnets and magnetic lines of force.

Fig.2. Unlike poles attract each other;
like poles repel each other.

  1. Each magnet has two poles called north pole (N) and south pole (S).
  2. Unlike poles attract, like poles repel.
  3. A force field exists, around a magnet which is concentrated at the poles of the magnet. The strength of the magnetic field is indicated by the density or concentration of lines of force.
  4. Lines of force repel each other.
  5. Lines of force cannot intersect.
  6. Lines of force form closed loops.