The strength of an electromagnet depends on:
(i) The number of turns in the coil. If we increase the number of turns in the coil, the strength of electromagnet increases.
(ii) The current flowing in the coil. If the current in the coil is increased, the strength of electromagnet increases.
(iii) The length of air gap between its poles.
|Bar magnet (or Permanent magnet)||Electromagnet|
|1. The bar magnet is a permanent magnet.||1. An electromagnet is a temporary magnet. Its magnetism is only for the duration of current passing through it. So, the magnetism of an electromagnet can be switched on or switched off as desired.|
|2. A permanent magnet produces a comparatively weak force of attraction.||2. An electromagnet can produce very strong magnetic force.|
|3. The strength of a permanent magnet cannot be changed.||3. The strength of an electromagnet can be changed by changing the number of turns in its coil or by changing the current passing through it.|
|4. The (north-south) polarity of a permanent magnet is fixed and cannot be changed.||4. The polarity of an electromagnet can be changed by changing the direction of current in its coil.|
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