Control System Components Question and Answers

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 Control System Components

Industrial Control Devices:

Switches

1.The contact resistance of a manually operated switch is
   A. Zero
   B. Very high
   C. Very low
   D. None of the above
Answer: Very low
 2. Which one of these is not a manually operated switch?
   A. Thumbwheel switch
   B. Rotary selector switch
   C. Crossbar switch
   D. Toggle switch
Answer: Crossbar switch
 3. A switch should have
   A. High insulation resistance
   B. Low insulation resistance
   C. Insulation resistance equal to contact resistance
   D. None of the above
Answer: High insulation resistance
4. A Thumbwheel switch
   A. Has an operating wheel which has numbers on it
   B. Is an alternative form of rotary switch
   C. Requires half the operating torque required in a rotary switch
   D. Supports the features A, B and C
Answer: Supports the features A, B and C
5.  When a membrane key switch is pressed
   A. The row conductor sheet gets separated from the column contact conductor sheet
   B. The row conductor sheet comes into contact with column conductor sheet
   C. A plunger exerts a pressure on the carbon button and it touches the contact print on the circuit board
   D. None of the above
Answer: The row conductor sheet comes into contact with column conductor sheet

Relays

1.A single phasing relay can be used with
a) 1ɸ motor
b) 2r ɸ motor
c) 3 ɸ motor
d) All of these
Answer: 3 ɸ motor
2. A relay is used to
a) Break the fault current
b) Sense the fault
c) Sense the fault and direct to trip the circuit breaker
d) All of these
Answer: Sense the fault and direct to trip the circuit breaker
3. In impedance relay, current element torque should be
 a) Equal to voltage element torque
b) Greater than voltage element torque
c) Less than voltage element torque
d) None of these
Answer: Equal to voltage element torque
4. Over current fault is most likely in
a) Transformer
b) Overhead line equipment
c) Alternator
d) Motors
Answer: Overhead line equipment
5. Plug setting of a relay can be changed by changing
a) Air gap
b) Back up stop
c) Number of ampere turns
d) All of these
Answer: Number of ampere turns
6. Distance relays are generally
a) Impedance type
b) MHO type
c) Reactance type
d) All of these
Answer: MHO type
7. Buchholz relay is used to protect against
a) Inter-turn fault
b) External faults
c) Rotor faults
d) Every internal faults
Answer: Every internal faults
8. Instantaneous relay should operate within
a) 0.0001 sec
b) 0.001 sec
c) 0.01 sec
d) 0.1 sec
Answer: 0.01 sec
9. MHO relay is inherently a
a) Directional type
b) Non-directional type
c) Unidirectional type
d) None of these
Answer: Directional type
10. Basic relay connection requirement is that the relay must operate for
a) Load
b) Internal faults
c) Both (a) and (b)
d) None of these
Answer: Internal faults
11. An impedance relay is used for
a) Earth faults
b) Interphase faults
c) Both (a) and (b)
d) None of these
Answer: Both (a) and (b)
12. Relay gets its operating energy from
a) Transformer
b) Alternator
c) Overhead lines
d) C.T., P.T.
Answer: C.T., P.T.
13. Good relay should possess
a) Speed & reliability
b) Aped & sensitivity
c) Adequateness & selectivity
d) All of these
Answer: All of these
14. Earthing transformer is used to
a) Improve neutral wire’s current capacity
b) Avoid overheating of transformer
c) Provide artificial earthing
d) Avoid harmonics
Answer: Provide artificial earthing
15. Percentage differential protection is used to prevent against
a) Inter-turn faults
b) Heavy Loads
c) External Faults
d) Magnetizing current
Answer: Magnetizing current
16. Back up protection is needed for
a) Over voltage
b) Short circuits
c) Over current
d) All of these
Answer: Short circuits
17. An instantaneous relay is
a) Permanent moving magnet
b) Induction cup
c) Shaded pole
d) Moving coil
Answer: Permanent moving magnet
18. Relays for transmission line protection are
a) In three zones
b) In two zones
c) Independent of zone
d) None of these
Answer: In three zones
19. Induction cup relays responds to
a) Current
b) Power
c) Voltage
d) Impedance
Answer: Impedance
20. Split-phase relay responds to
a) Over load faults
b) Over voltage
c) Inter turn faults
d) All of these
Answer: Inter turn faults
21. Time classification of relays includes
a) Instantaneous relays
b) Definite time lag
c) Inverse time lag
d) All of these
Answer: All of these
22. Directional relays responds to
a) Power
b) Voltage
c) Current
d) Reactance
Answer: Power
23. Single phase preventers are used for
a) Transmission lines
b) Transformers
c) Motors
d) Underground cables
Answer: Motors
24. In carrier current protection, wave trap is used is for trapping
a) High frequency waves entering in generating units
b) Power frequency waves
c) Both (a) and (b)
d) None of these
Answer: High frequency waves entering in generating units
25. Operating current in relay is
a) A.c. only
b) D.c. only
c) Both (a) and (b)
d) None of these
Answer: Both (a) and (b)
26. For phase fault on long line, which relay is used?
a) MHO relays
b) Reactance relays
c) Impedance relays
d) All of these
Answer: Impedance relays
27. For motor protection, which relay is used?
a) Thermocouple type relays
b) Bimetallic relays
c) Electronic relays
d) All of these
Answer: All of these
28. For protection against synchronizing power surges, which relay is used?
a) Split-phase relays
b) Impedance relays
c) Reactance relays
d) MHO relays
Answer: MHO relays
29. Pilot wire protection is for
a) Overhead lines
b) Transformer
c) Motors
d) Cables
Answer: Overhead lines
30. Under voltage relays are used for
a) Motors
b) Alternators
c) Bus bars
d) All of these
Answer: All of these
31. In an impedance relay, fault current is maximum if fault occurs near the
a) Relay
b) Center of the line
c) Transformer
d) None of these
Answer: Relay
32. More faults occur in
a) Generators
b) Under ground cables
c) Transformers
d) Over head lines
Ans: Over head lines
33. Actual tripping of a static relay is obtained by
a) SCR
b) Thyristors
c) UJT
d) None of these
Answer: None of these
34. Instantaneous relay is
a) Hinged armature type
b) Polarized type
c) Balanced beam type
d) All of these
Answer: Hinged armature type
35. It is possible to work on ungrounded systems of 11 kV for a length of
a) 10 Kms
b) 50 Kms
c) 90 kms
d) 110 Kms
Answer: 110 Kms
36. Advantage of grounded neutral is
a) Persistent arcing grounds are eliminated
b) Earth fault are utilized to disconnect the fault
c) Both (a) and (b)
d) None of these
Answer: Both (a) and (b)
37. Neutral can be grounded by
a) Solid grounding
b) Resistance grounding
c) Reactance grounding
d) All of these
Answer: All of these
38. Thyrite is used in lightning arrestors because of its
a) Straight line characteristic
b) Non-linear characteristic
c) None of these
d) All of these
Answer: Non-linear characteristic
39. Location of lightning arrestor is
a) After the transformer
b) After the distributor
c) Before the transformer
d) None of these
Ans: Before the transformer
40. Lightning arrestors are
a) Surge reflectors
b) Surge divertors
c) Surge absorbers
d) Surge attenuators
Ans: Surge divertors
41. Relays for transmission line protection are
a) In three zones
b) In two zones
c) Independent of zone
d) None of these
Ans: In three zones

Pneumatics

1. Fluid power circuits use schematic drawings to:
a) Simplify component function details
b) Make it so only trained persons can understand the functions
c) Make the drawing look impressive
d) Make untrained person to understand
Answer: Simplify component function details
2. A pneumatic symbol is:
a) Different from a hydraulic symbol used for the same function
b) The same as a hydraulic symbol used for the same function
c) Not to be compared to a hydraulic symbol used for the same function
d) None of the mentioned
Answer: Different from a hydraulic symbol used for the same function
3. Pneumatic systems usually do not exceed:
a) 1 hp
b) 1 to 2 hp
c) 2 to 3 hp
d) 4 to 5 hp
Answer: 1 hp
4. Most hydraulic circuits:
a) Operate from a central hydraulic power unit
b) Use air-over-oil power units
c) Have a dedicated power unit
d) Does not have dedicated power unit
Answer: Operate from a central hydraulic power unit
5. Hydraulic and pneumatic circuits:
a) Perform the same way for all functions
b) Perform differently for all functions
c) Perform the same with some exceptions
d) Does not perform all the functions
Answer: Perform the same with some exceptions
6. The lubricator in a pneumatic circuit is the:
a) First element in line
b) Second element in line
c) Last element in line
d) Third element in line
Answer: Last element in line
7. Series circuits work on both hydraulic and pneumatic actuators.
a) True
b) False
Answer: False
8. When comparing first cost of hydraulic systems to pneumatic systems, generally they are:
a) More expensive to purchase
b) Less expensive to purchase
c) Cost is same
d) Cost is not required
Answer: Less expensive to purchase
9. When comparing operating cost of hydraulic systems to pneumatic systems, generally they are.
a) More expensive to operate
b) Less expensive to operate
c) Cost is same to operate
d) Cost is not required
Answer: Less expensive to operate
10. The most common hydraulic fluid is:
a) Mineral oil
b) Synthetic fluid
c) Water
d) Gel
Answer: Water

Hydraulic Systems

1. Heavy lifting work is often accomplished by shifting fluids in big machines. The power system of such machines can be described as
a) Reciprocating
b) Pneumatic
c) Hydraulic
d) Hybrid
Answer: Hydraulic
2. The scientific principle that makes hydraulic systems possible is
a) Pascal’s principle
b) Boyle’s law
c) Bernoulli’s principle
d) The fluid flow principle
Answer: Pascal’s principle
3. Pneumatic and other power systems can support three kinds of motion; they are
a) Linear, reciprocating, and random motion
b) Linear, flowing, and rotary motion
c) Linear, zigzag, and spiral motion
d) Linear, reciprocating, and rotary motion
Answer: Linear, reciprocating, and rotary motion
4. A single acting cylinder can be pressurized externally from one direction only.
a) True
b) False
Answer: True
5. A one-way valve that lets air into the reservoir of a compressor, but doesn’t let it out, is a
a) Check valve
b) Receiver valve
c) Control valve
d) Three way valve
Answer: Check valve
6. Series circuits work on both hydraulic and pneumatic actuators.
a) True
b) False
Answer: True
7. 5/2 way single solenoid valve has:
a) 2 ports 2 positions
b) 5 ports 2 positions
c) 5 ports 5 positions
d) 2 ports 5 positions
Answer: 5 ports 2 positions
8. The ____________________ converts the compressed air energy into mechanical energy in the form of linear movement in one direction only.
a) Piston cylinders
b) Double acting cylinders
c) Single acting cylinders
d) Hydraulic pumps
Answer: Single acting cylinders
9. A _____________ restricts air flow.
a) Throttle valve
b) Shuttle valve
c) Directional control valve
d) Single acting cylinder
Answer: Throttle valve
10. When the piston area of the cylinder is connected to the atmosphere, the piston of the single-acting cylinder is pressed by the spring to the ________________
a) Cylinder center
b) Cylinder down
c) Cylinder bottom
d) Cylinder upper
Answer: Cylinder center

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