The thermal conductivity of hydrogen is _____________ times that of air?

Related Mcqs:

1. Hydrogen has a heat transfer co-efficient __________ times that of air?

   A. 1.5 B. 2.5 C. 3.5 D. 4.5...

2. The density of hydrogen is __________ times the density of air?

   A. 0.07 B. 1.5 C. 2.5 D. 3.5...

3. With conventional hydrogen cooling it is possible to increase the rating of a single unit to___________?

   A. 50 MW B. 100 MW C. 200 MW D. none of the above...

4. Which of the following is an advantage of hydrogen cooling ?

   A. Increase in efficiency B. Increase in ratings C. Increase in life D. Smaller size of coolers E. All of the above...

5. In direct cooled system using hydrogen both stator and rotor conductors are made____________?

   A. solid B. hollow C. perforated D. any ofthe above...

6. The length cf air gap to be provided in __________ is primarily determined by power factor consideration?

   A. d.c. series motor . B. d.c. shunt motor C. induction motor D. synchronous motor...

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

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

8. The operation of a D.C. machine with large air gap lengths is comparatively_____________?

   A. quiet B. noisy C. either of the above D. none of the above...

9. For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used?

   A. 1.0 to 1.2 A/mm2 B. 1.5 to 2.0 A/mm2 C. 2.2 to 3.2 A/mm2 D. 3.2 to 4.2 A/mm2...

10. The forced oil and air circulation method is usual one for transformers of capacities____________?

    A. upto 5 MVA B. upto 10 MVA C. upto 20 MVA D. 30 MVA upwards...