Examples of systems that generate C-EMF?

[Miyz]

Hi,Do you know systems that generate C-EMF?
Set ups like an Electric Motor? What other system do you have in mind?

Another thing.
I know that CEMF is caused by a changing electromagnetic field. How can an electromagnetic field be changed? Please elaborate! Miyze,

 

[Drakkith]

A simple inductor generates a counter EMF when the current through it is changing. This change in current flow causes the magnetic field produced by the current to change in magnitude. When the magnitude changes the field induces an EMF in the coils of the inductor that is opposite to the applied EMF driving the current flow.

As for a changing EM field, it's simply that the magnitude of the field must change or the position in a non-uniform field must change. So when you move a magnet into a coil the magnetic field through the coil is changing as the magnet approaches, which induces a current through the coil.