Hans Oersted, in 1820, first discovered that when an electric current is passed through a conducting wire, a magnetic field is produced around it. The Earth's magnetic field is uniform in a limited space. In case the field lines are parallel and equidistant, these represent a uniform magnetic field. The magnetic field lines never intersect each other because if they do so, these would be two directions of magnetic field at that point, which is not possible. The magnetic field lines are crowded near the pole where the magnetic field is strong and are far apart near the middle of the magnet and far from the magnet where the magnetic field is weak. Whereas inside the magnet, the field lines are directed from south pole to north pole. By repeating the above process from the same pole of the magnet but different points, other magnetic field lines can be traced.Ī magnetic field line is a closed and continuous curve.Ī magnetic field line is directed from North Pole to South Pole outside the magnet. This smooth curve represents a magnetic field line. Repeat this process of moving the needle and marking dots at its two ends till its South Pole reaches the North Pole of the magnet. Mark the position of the other end(s) with a dot. Now move the compass in such a manner that one end (N) of the needle coincides with the second pencil dot. Now place a small compass needle close to South Pole of the magnet and mark two pencil dots at two ends of the needle. Place a bar magnet and mark its boundary. Take a paper sheet and fix it on a drawing board by pins. TRACING MAGNETIC FIELD LINES OF A BAR MAGNET USING A MAGNETIC COMPASS: The iron filings are found to arrange themselves in a pattern.
To know the magnetic lines of forces, place a magnet on a cardboard sheet and gently sprinkle some iron filings uniformly over it. These lines are called magnetic lines of forces. These are the curved paths along which magnetic force is acting on them in the magnetic field of the bar magnet. We can describe the magnetic field around a magnet by magnetic field lines. All magnets have a space around them in which the force of attraction and repulsion can be detected.
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