Back emf....PLEASE EXPLAIN (1 Viewer)

[enter~space~cap]

ok according to various textbooks, it says something liek

"the induced emf must oppose the supplied emf driving the coil"....

can anyone explain to me in terms of back emf in DC motos what is meant by the "induced emf" and the "supplied emf"???

My guess is that the 'supplied emf' is the fact that the stator coils causes the rotor coils to rotate because a current passes through it. And the definition of 'induced coil' is that because the coil is rotating in the magnetic field another emf is created in the form of currents opposing 'something'....please correct me on these

Thanks in advance

 

[kimmeh]

this is straight from my notes. i dont know if you'd get it straight away though or answers your question :

Electric motors use an external emf applied to the coils to produce an electric current in the coils positioned in an external magnetic field. This current produces a magnetic field that interacts with the external magnetic field. As the coils rotate in the external magnetic field, an emf is induced in the coils due to the constantly changing magnetic flux threading the coils. By Lenz's Law, this induced emf is in the opposite direction to the external supply emf causing the rotation, and it has the effect of reducing the net emf applied to the coils. Because the induced emf is in the opposite direction to the supply EMF, it is known as the back EMF

it took me a while to understand this. actually, i'm still a bit unclear of it

 

[enter~space~cap]

thanks!

 

[The Bograt]

If you implement the Law of Conservation of Energy you will see that if a current was produced in the same direction as the flux change then it would produce more current forwards, which would turn the motor faster, and faster, and faster etc. creating a perfectly efficient perpetual motion machine

Don't know how much that helps, just putting things in perspective