Que-Ans of DC Generator

1. Q. What is Residual Magnesium?
2. Q. What is armature reaction in DC Generator ?
3. Q. What is the reason of the generated emf reduce while increase the load current ? 
4. Q. At no load what is relation between Ideal and practical characteristics ? Why ?  
5. Q. What is the value of field winding resistance ? Why is So ?
6. Q. What is reason to fail DC Generator as self excite ?
7. Q. If load of Dc Generator is disconnect, what is effect on induced emf  ?