21. When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be

A. choked
B. underdamping
C. overdamping
D. none of these

22. The ratio of the workdone on the blades to the energy supplied to the blades is called

A. blading efficiency
B. nozzle efficiency
C. gross or stage efficiency
D. mechanical efficiency

23. The discharge is __________ at critical pressure.

A. zero
B. minimum
C. maximum

24. The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop

A. remains the same
B. increases
C. decreases
D. is unpredictable

25. The steam leaves the nozzle at a

A. high pressure and a low velocity
B. high pressure and a high velocity
C. low pressure and a low velocity
D. low pressure and a high velocity

26. The critical pressure gives the velocity of steam at the throat

A. equal to the velocity of sound
B. less than the velocity of sound
C. more than the velocity of sound
D. none of these

27. The Parsons’ reaction turbine has

A. only moving blades
B. only fixed blades
C. identical fixed and moving blades
D. fixed and moving blades of different shape

28. The action of steam in a steam turbine is

A. static
B. dynamic
C. static and dynamic
D. neither static nor dynamic

29. The blade velocity coefficient is ratio of relative velocity of steam at outlet tip of the blade to the relative velocity of steam at inlet tip of the blade.

A. True
B. False

30. Multi-stage steam turbines are of the

A. velocity compounded type
B. reaction type
C. pressure compounded type
D. all of these