The density of hydrogen is __________ times the density 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 thermal conductivity of hydrogen is _____________ times that of air?

   A. 2 B. 3 C. 5 D. 7...

3. 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...

4. A current density of __________ is ilsed for large power transformers with forced circulation of oil or with water cooling coils?

   A. 1.5 to 2.5 A/mm2 B. 3.5 to 4.5 A/mm2 C. 4.0 to 5.0 A/mm2 D. 5.4 to 6.2 A/mm2...

5. 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...

6. 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...

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

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

8. The noise produced by a ___________ cooled machine is less as the rotor moves in a medium of smaller density?

   A. air B. hydrogen C. either A. or B. D. none of the above...

9. Which of the following brushes can be used for high values of current density ?

   A. Metal graphite brushes B. Hard carbon brushes C. Electro-graphitic brushes D. Natural graphite brushes...

10. For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?

    A. 1.0 Wb/m2 B. 1.1 Wb/m2 C. 1.3 Wb/m2 D. 1.6 Wb/m2 E. None of the above...