Armature reaction of an unsaturated D.C. machine is_____________?

Related Mcqs:

1. The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be_____________?

   A. 640 V
   B. 620 V
   C. 600 V
   D. 580 V

2. Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be_______________?

   A. 2 : 3
   B. 3 : 1
   C. 3 : 2
   D. 1 : 3

3. Open circuited armature coil of a D.C. machine is________________?

   A. identified by the scarring of the commutator segment to which open circuited coil is connected
   B. indicated by a spark completely around the commutator
   C. both A. and (b)
   D. none of the above

4. The demagnetising component of armature reaction in a D.C. generator___________?

   A. reduces generator e.m.f.
   B. increases armature speed
   C. reduces interpoles flux density
   D. results in sparking trouble

5. In a separately excited generator supplying rated load the armature reaction.

   A. is always present
   B. is always absent
   C. may be sometimes present
   D. none of the above

6. Armature reaction in a generator results in_____________?

   A. demagnetisation of leading pole tip and magnetisation of trailing pole tip
   B. demagnetisation of trailing pole tip and magnetisation of leading pole tip
   C. damagnetising the center of all poles
   D. magnetising the center of all poles

7. As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately______________?

   A. 40 percent
   B. 25 percent
   C. 10 percent
   D. 5 percent

8. Armature coil is short circuited by brushes when it lies_____________?

   A. along neutral axis
   B. along field axis
   C. in any of the above positions
   D. in none of the above positions

9. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is______________?

   A. 2
   B. 4
   C. 6
   D. 8

10. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be_____________________?

    A. 270 V
    B. 267.5 V
    C. 265 V
    D. 257.4 V