Question (1) a) Describe with a neat sketch, the construction of a DC machine. b) Derive from the first principle, an expression for the torque developed in DC machine. c) Derive from the first principle, an expression for the generated voltage in DC machine. d) Explain with neat sketches, the basic action of a commutator. e) With neat diagrams explain the phenomenon of armature reaction in a DC machine f) Explain why compensating winding and inter-poles are used in a DC machine 9) Explain the critical field resistance in a DC shunt generator and the method of determining it. h) Draw the load characteristic for separate and shunt excitation in the same coordinates with common I axis. 1) Using the graphs in the previous part and equivalent schematics of a shunt de generator and a separately excited dc generator explain why for shunt generators, the terminal voltage V drops off more as the load increases, as compared to the voltage drop off occurring in separately excited generators. J) How does the voltage regulation of a dc shunt generator compare to that of a separately excited dc generator? K) What are advantages and drawbacks of de shunt and separately excited generators?