Electrical Engineering ⇒ Topic : Lifting Power of a Magnet
Lifting Power of a Magnet
When two opposite polarity magnetic poles are separated by a short distance in air, there is a force of attraction tending to pull the two poles together. The magnitude of this force can be calculated in terms of flux density in the air gap and cross-sectional area of the pole.
Consider two poles, north and south, each of area 'a' square metres separated by a short distance in air as shown in Fig. (a). Let P newtons be the force of attraction between the two poles. If one of the poles, say S-pole, is pulled apart through a small distance dx, then work will have to be done against the force of attraction.
Note that P is the force of attraction at each pole. In a practical magnet, there are two poles See Fig. (b) so that total force of attraction is 2P. Electromagnets are widely used for commercial lifting jobs such as loading scrap iron into a truck or raising an armature to a higher position.
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