Monday, 12 February 2018

What Is Back EMF Its A Useful Or Not!?

What Is Back EMF Its A Useful Or Not!? 




All About Back EMF



when the armature of a dc motor rotates, in a Magnetic Field, its conductors cut the magnetic flux.




Therefore an emf is induced in them according to Faraday's laws of Electromagnetic Induction, whose direction is in opposition to the applied voltage (V)  as shown in figer.



Because of its opposing direction, it is called counter e.m.f or Back EMF (Eb).





when the armature of a dc motor rotates, an e mf is induced in armature conductors which opposes the applied voltage is known as back em f or counter e.m.f Its value is always less than the applied voltage.

Its value is the same as for the motionally induced Back EMF in the dc generator,

i.e. Eb = (§ZNP)/(60A)



The applied voltage (V) has to force current through the armature conductors against this Back EMF The electric workdone in overcoming this opposition is converted into mechanical energy developed in the armature.

Recommended Articles For Better Knowledge :


  • Energy conversion is not possible unless there is some opposition.
  • In dc generators, the opposition is provided by magnetic force and in dc motors, Back EMF does this job.


Question part about Back EMF:

1)when the armature of a dc motor rotates, in a magnetic field, its conductors cut the magnetic flux Therefore an emf is induced in them according to _______law?????
Ans:Faraday's laws of Electromagnetic induction,

2) what is the job of back emf in dc generator??? 
Ans:In dc generators, the opposition is provided by magnetic force and in dc motors, back e m f does this job.

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