In D.C. machines, the ________ in field mmf results in increase in size and cost of machines?

Related Mcqs:

1. In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made____________?

   A. equal to that of armature mmf
   B. less in comparison with the armature mmf
   C. large in comparison with the armature mmf
   D. none of the above

2. In _________ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft?

   A. small
   B. medium
   C. large
   D. any of the above.

3. Electrical machines having a power output up to about 750 W may be called__________machines?

   A. small size
   B. medium size
   C. large size
   D. any of the above

4. The design of mechanical parts is particularly important in case of __________ speed machines?

   A. low
   B. medium
   C. high
   D. any of the above

5. The action of electromagnetic machines can be related to which of the following basic principles __________?

   A. Induction
   B. Interaction
   C. Alignment
   D. All of the above

6. _______________is universally used for windings of electrical machines because it is easily workable without any possibility of fracture?

   A. Silver
   B. Steel
   C. Aluminium
   D. Copper

7. Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto_______________?

   A. 10 MW
   B. 30 MW
   C. 60 MW
   D. 150 MW

8. In D.C. machines the width of the duct is usually_____________?

   A. 4 mm
   B. 6 mm
   C. 8 mm
   D. 10 mm

9. In D.C. machines the usual limit of slot pitch is________________?

   A. between 5 to 10 mm
   B. between 10 to 15 mm
   C. between 15 to 20 mm
   D. between 25 to 35 mm

10. In D.C. machines the number of slots per pole usually lies___________?

    A. between 2 to 4
    B. between 6 to 8
    C. between 9 to 16
    D. between 20 to 30