question_answer 45)

  Commercial electric motors do not use (a) An electromagnet to rotate the armature (b) Effectively large number of turns of conducting wire in the current carrying coil (c) A permanent magnet to rotate the armature (d) A soft iron core on which the coil is wound

Answer:

                  (c) A commercial electric motor is one which uses the following (i) An electromagnet in place of permanent magnet. (ii) Large number of turns of the conducting wire in the current-carrying coil. (iii) A soft iron core on which the coil is wound. The combination of soft iron core and coil is called an armature. It enhances the power of motor. Thus, commercial electric motors do not use permanent magnet to rotate the armature because permanent magnets are weak and do not produce strong magnetic field in the region.