Question
Sun July 15, 2012 By:
 

what is the role of a magnet in an electric motor or a electric generator while the armature is rotated by the split ring commutator which is connected to the battery. it means that the armature is rotated by the battery? and what is the role of magnets in a speaker or any thing related with electromagnetic induction or mutual induction?

Expert Reply
Sun July 15, 2012
In Motor, the armature is rotated by a force called Lorentz Force. It is the force on charged particles in Electric of Magnetic fields. Thus a MAgnetic field is needed which is prodced by Magnet.
In Speakers, a spring is present above a magnet. In the coil current is passed. So depending on intensity of current, compression is produced in spring. This is used to vibrate a diaphram in Speakers made of metal caps or a fiber, thus produce sound.
 
Hence we see that in such devices magnet is used to produce magnetic field.A
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