Online Practice Electrical Machine Design - Set 07 - ObjectiveBooks

Online Practice Electrical Machine Design - Set 07

Practice Test: Question Set - 07

1. Yokes with rectangular cross-section are used for
    (A) Small capacity transformers
    (B) Medium capacity transformers
    (C) Large capacity transformers
    (D) Any of the above

2. Which of the following methods is most accurate?
    (A) Equivalent current method
    (B) Equivalent power method
    (C) Equivalent torque method
    (D) Method of average losses

3. The increase in heat dissipation by air blasts is due to increase in
    (A) Conduction
    (B) Convection
    (C) Radiation
    (D) Any of the above

4. 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

5. 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

6. The thermal conductivity of hydrogen is ______ times that of air
    (A) 2
    (B) 3
    (C) 5
    (D) 7

7. The flash point of transformer oil should be higher than
    (A) 40°C
    (B) 60°C
    (C) 80°C
    (D) 104°C

8. Is usually used for brush rockers
    (A) Mild steel
    (B) Copper
    (C) Aluminium
    (D) Cast-iron

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 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

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