1. What is a centrifugal pump?
2. Mention 4 applications of a centrifugal pump.
3. What is pressure head? What is its units?
4. Write 4 criteria based on which you will select a centrifugal pump?
5. What is the material of the impeller in a centrifugal pump?
6. What is a self-priming centrifugal pump?
7. What happens when there is friction between the pipe wall and the fluid?
8. Mention at least 3 prime movers used in centrifugal pump.
9. How many meters of water is 1 bar?
10. Define rated speed of a centrifugal pump.
11. A circuit breaker is
(A) power factor correcting device
(B) a device to neutralize the effect of transients
(C) a waveform correcting device
(D) a current interrupting device.
12. The function of protective relay in a circuit breaker is
(A) to each any stray voltages
(B) to close the contacts when the actuating quantity reaches a certain predetermined value
(C) to limit arcing current during the operation of circuit breaker
(D) to provide additional safety in the operation of circuit breaker.
13. Low voltage circuit breakers have rated voltage of less than
(A) 220 V
(B) 400V
(C) 1000 V
(D) 10,000 V.
14. The fault clearing time of a circuit breaker is usually
(A) few minutes
(B) few seconds
(C) one second
(D) few cycles of supply voltage.
15. Which of the following circuit breakers is preferred for EHT application
(A) Air blast circuit breakers
(B) Minimum oil circuit breakers
(C) Bulk oil circuit breakers
(D) SF6 oil circuit breakers.
16. Which of the following is not a type of the contactor for circuit breakers ?
(A) Electro-magnetic
(B) Electro-pneumatic
(C) Pneumatic
(D) Vacuum.
17. SF6 gas is
(A) sulphur fluoride
(B) sulphur difluoride
(C) sulphur hexafluorine
(D) sulphur hexafluoride.
18. SF6 gas
(A) is yellow in color
(B) has pungent odor
(C) is highly toxic
(D) is non-inflammable
19. The pressure of SF6 gas in circuit breakers is of the order of
(A) 100 mm Hg
(B) 1 kg/cm2
(C) 3 to 5 kg/cm2
(D) 30 to 50 kg/cm2.
20. While selecting a gas for circuit breaker, the property of gas that should be considered is
(A) high dielectric strength
(B) non-inflammability
(C) non-toxicity
(D) all of the above.
21. The following figure shows the voltage waveform across the pole of a circuit breaker; In this
voltage B represents
22.
(A) System voltage
(B) Re striking voltage
(C) Recovery voltage
(D) Extinction of arc.
23. In the above figure, D represents
(A) Recovery voltage
(B) Re striking voltage
(C) System voltage
(D) Extinction of arc.
24. In the above figure, A represents
(A) Recovery voltage
(B) Re striking voltage
(C) System voltage
(D) Extinction of arc.
25. In the above figure, c represents
(A) Recovery voltage
(B) Re striking voltage
(C) System current
(D) Extinction of arc.
26. Ionization in circuit breakers is facilitated by
a) Increase of field strength
b) Increase of mean free path
c) High temperature
d) All of these
27. Part of circuit breaker helpful in breaking the current is
a) Trip Coil
b) Contacts
c) Handle
d) Medium
28. Desired tripping of a circuit breaker is
a) Manually
b) automatically
c) That it should give warning
d) None of these
29. Arcing time is the time between
a) Separation of circuit breaker and extinction of arc
b) Separation of circuit breaker and rise of recovery voltage
c) Normal current interruption and arc extinction
d) None of these
30. Arc interruption is done by
a) High resistance interruption
b) current zero interruption
c) Both (a) and (b)
d) None of these
31. In circuit breaker, to facilitate arc quenching, dielectric strength can be increased by
a) Lengthening of the gap
b) Cooling
c) Blast effect
d) All of these
32. An ideal circuit breaker should offer
a) Zero & infinite impedance before & after interruption respectively
b) Infinity & zero impedance before & after interruption respectively
c) Equal impedance before & after interruption
d) None of these
33. Which circuit breaker is preferred to be installed in extra high voltage ac system?
a. Bulk oil type circuit breaker
b. Air blast circuit breaker
c. SF6 circuit breaker
d. Vacuum circuit breaker
34. Which of the following circuit breakers is highly reliable and has a least maintenance?
a. Oil circuit breakers
b. Air blast
c. Vacuum circuit breakers
d. SF6 circuit breakers
35. The breaking capacity of a circuit breaker in MVA (3 phase) is given by
(A) rated service voltage x rated symmetrical current
(B) 1.1 x rated service voltage x rated symmetrical current
(C) (2)1/2 x rated service voltage x rated symmetrical current
(D) (3)1/2x rated service voltage x rated symmetrical current.
36. Which curve in the figure represents inverse time characteristics ?
(A) Curve A
(B) Curve B
(C) Curve C
(D) Curve D
37. Fuse protection is used for current ratings up to
(A) 10 A
(B) 20 A
(C) 50 A
(D) 100 A.
38. The fuse current in amperes is related with fuse wire diameter D as
(A) I ∞ I/D
(B) I ∞ D
(C) I ∞ D3/2
(D) I ∞ D2.
39. The acting contacts for a circuit breakers are made of
(A) Stainless steel
(B) Hard pressed carbon
(C) Porcelain
(D) Copper tungsten alloy.
40. Ionization in a circuit breaker is not facilitated by
(A) high temperature of surrounding medium
(B) material of contacts
(C) increase of field strength
(D) increase of mean free path.
28. Which circuit breaker is generally used in railway traction ?
(A) SF6 gas circuit breaker
(B) Air break circuit breaker
(C) Vacuum circuit breaker
(D) Minimum oil circuit breaker.
41. The number of cycles in which a high speed circuit breaker can complete its operation is
(A) 3 to 8
(B) 10 to 18
(C) 20 to 30
(D) 40 to 50.
42. Breaking capacity of a circuit breaker is usually expressed in terms of
(A) Amperes
(B) Volts
(C) MW
(D) MVA.
