The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?

Related Mcqs:

1. The mcrease in heat dissipation by air blasts is due to increase in______________?

   A. conduction
   B. convection
   E. radiation
   D. any ofthe above

2. Electrical machines having power outputs ranging from a few kW up to approximately 250 kW may be classified as_____________?

   A. small size machines
   B. medium size machines
   C. large size machines
   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. _______________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

5. By which of the following methods the temperature rise of windings and other parts may be determined ?

   A. Thermometer method
   B. Resistance method
   C. Embedded temperature detector method
   D. Any of the above

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

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

7. The efficiency of a machine should be as ____________ as possible to reduce the operating cost?

   A. high
   B. low
   C. either of the above
   D. none of the above

8. In a D.C. machine, the value of peripheral speed should not, normally, exceed___________?

   A. 10 m/s
   B. 20 m/s
   C. 30 m/s
   D. 40 m/s

9. In a D.C. machine the number of brush arms is _________ the number of poles?

   A. less than
   B. equal to
   C. greater than
   D. none of the above

10. The laminations of the armature of a D.C. machine are usually ___________ thick?

    A. 0.1 to 0.2 mm
    B. 0.2 to 0.3 mm
    C. 0.3 to 0.4 mm
    D. 0.4 to 0.5 mm