Since we do not fully understand what a magnetic field is, we simply say that it is a condition of space. The presence of a magnetic field is detected by its effects, such as those on an electric current, or on iron filings, or on a permanent magnet. The direction in which the magnetic field acts at a particular point is given by the direction in which the force would act on an isolated north-seeking pole (a N-pole) at that point. The theoretical concept of an isolated north pole is one which is used simply to define certain aspects of magnetic fields. When we refer to a N-pole, we imply that the pole experiences a force in the earth’s magnetic field towards the earth’s north pole. Similarly, a S-pole is a south-seeking pole.
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