Bar Magnets

• The bar magnet is a permanent magnet.
  
• It produces a comparatively weak force of attraction.
  
• The strength of a bar magnet cannot be changed.
  
• The polarity of a bar magnet is fixed and cannot be changed.
  

Electromagnets

• An electromagnet is a temporary magnet.
  
• It produces a very strong magnetic force.
  
• 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.
  
• The polarity of an electromagnet can be changed by changing the direction of current in its coil.