About back emf

There's a ton of stuff out there on google.

http://www.magnet.fsu.edu/education/tutorials/java/backemf/index.html

I hope this isn't for homework.

When in doubt, ask your professor (and that goes for the next thread too)

http://www.magnet.fsu.edu/education/tutorials/java/backemf/index.html

this link explain this topic in clarity ..

neweng_26

hi

the Back EMF is like opposing EMF, when can u move on road ? if there is no friction between two moving things, they can't move, similarly to run the motor some opposing force must be needed and that is Back EMF.

Divyesh patel

guru_88,

My Dad called 'back EMF' "counter EMF" (CEMF). When a coil turn induces voltage in a second coil turn, the direction of the voltage is opposite and (almost) equal.

This is true even when considering the situation of a primary winding of a transformer by itself. This is the reason that a utility can energize an unloaded transformer with nothing more of a result than a faint 'hummm' and a tiny bit of heat. In reality, the primary coil is just a copper wire, that if straightened out, would melt and vaporize if energized at the same voltage. The two voltages (and resultant currents) are opposing to an (almost) stand-still.

When current is drawn from a secondary load coil, the direction of the current is opposite in relation to the primary current and voltage direction.

Recognize that a motor is a generator even while running, but generates in the opposite direction, which is in line with the nature of induction.

CEMF is the reason a DC motor will speed up until it reaches a certain speed unloaded, when it would otherwise theoretically just keep speeding up. It achieves a balance between the EMF and the CEMF (almost).

The "almost" addresses the resistive currents and other energy and physical components not related directly to induction, but which are required for the operation.

I know that I may have opened up more questions for you than answers, and that others on the forum will have different detailed explanations, but this will start you in the direction of discovery that will result in your own conceptualization of how the forces are created, and that there is balance between the pusher and pushed.

Regards, CJM

Back-EMF is the motor behaving a bit like a generator.

It is called CEMF in USA Counter EMF Google that.