Legal Metrology • Paper-III
When a line commutated converter operates in the inverter mode, it
A)
draws both real and reactive power from the ac supply
B)
delivers both real and reactive power to the ac supply
C)
delivers real power to the ac supply
D)
draws reactive power from the ac supply
Correct option: C — delivers real power to the ac supply. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
In an AM system, for satisfactory operation, carrier frequency must be n times the bandwidth of message-signal. What is the value of n?
A)
> 2
B)
> 5
C)
> 10
D)
> 50
The information to be communicated is called the message.
Legal Metrology • Paper-III
Which one of the following statements is correct? The capacitor charging time in the AM envelope demodulator is based on the time for one
A)
half cycle of the carrier frequency
B)
quarter cycle of the carrier frequency
C)
half cycle of the lowest audio frequency
D)
quarter cycle of the highest audio frequency
The capacitor charging time is selected relative to the carrier and audio envelopes so it follows the audio without excessive ripple; the supplied option corresponds to the standard criterion.
Legal Metrology • Paper-III
In a commutation circuit employed to turn off an SCR, satisfactory turn-off is obtained when
A)
circuit turn-off time < device turn-off time
B)
circuit turn-off time > device turn-off time
C)
circuit time constant > device turn-off time
D)
circuit time constant < device turn-off time
Correct option: B — circuit turn-off time > device turn-off time. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
To prevent overloading of the last IF amplifier in a receiver, one should use
A)
Squelch
B)
Variable sensitivity
C)
Variable selectivity
D)
Double conversion
Correct option: A — Squelch. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
If the amplitude of the gate pulse to thyristor is increased then
A)
both delay time and rise time would increase
B)
the delay time would increase but the rise time would decrease
C)
the delay time would decrease but the rise time would increase
D)
the delay time would decrease while the rise time remains unaffected
Correct option: D — the delay time would decrease while the rise time remains unaffected. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The Q output of a J-K flip-flop is ‘1’. The output does not change when a clock-pulse is applied. The inputs J and K will be respectively (X-denotes don’t care state)
A)
0 and X
B)
X and 0
C)
1 and 0
D)
0 and 1
With Q=1 unchanged, J= X and K=0 is a hold condition.
Legal Metrology • Paper-III
In forward-bias portion of the thyristor’s i-v characteristic, the number of stable operating regions is
A)
One
B)
Two
C)
Three
D)
None
Correct option: B — Two. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-II
In hydro power stations, what is an enlarged body of water just above the intake and used as a regulating reservoir, called?
A)
Spillways
B)
Forebay
C)
Reservoir
D)
Penstock
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'Spillways' (Option A).
Legal Metrology • Paper-II
The leakage reactance of a three phase alternator determined by performing
A)
Open circuit and zero power factor tests
B)
Zero power factor and slip tests
C)
Open circuit and short circuit tests
D)
Short circuit and slip tests
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'Open circuit and short circuit tests' (Option C).
Legal Metrology • Paper-II
The use of high speed CB
A)
reduces the short circuit current
B)
improves system stability
C)
decreases system stability
D)
increases the shorter circuit current
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'reduces the short circuit current' (Option A).
Legal Metrology • Paper-II
Which of the following statements is/are correct? In pumped storage power plants
A)
water is recirculated through water turbines
B)
reversible turbines are used which operates as turbines for power generation during peak load hours and as pumps for pumping water during peak-off hours
C)
plain Francis turbines are used
D)
both (a) and (c) above are employed
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'water is recirculated through water turbines' (Option A).
Legal Metrology • Paper-II
If the speed of a d.c. motor increases with load torque, then it is a
A)
series motor
B)
permanent magnet motor
C)
differentially compounded motor
D)
cumulatively compounded motor
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'permanent magnet motor' (Option B).
Legal Metrology • Paper-II
Consider the following statements regarding HVDC transmission:
1. The modern HVDC systems use 12-pulse converter
2. DC systems never use ground or sea return
3. Most of present day d.c. schemes are two-terminal links
Which of the statements given above is/are correct?
A)
1, 2 and 3
B)
1 only
C)
2 and 3 only
D)
1 and 3
Correct option: D — 1 and 3. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-II
The response c(t) to a system is described by the differential equation d²c(t)/dt² + 4dc(t)/dt + 5c(t) = 0, the system response is:
A)
undamped
B)
underdamped
C)
critically damped
D)
oscillatory
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'oscillatory' (Option D).
Legal Metrology • Paper-II
When a ‘pumped station’ power plant is operated in conjunction with a steam power plant
A)
The operating cost of the steam plant becomes optimum
B)
Load factor of the steam plant is increased
C)
Chances of the tripping of the system decrease because of the use of two heterogeneous types of plants
D)
Operation of the storage plant in the pumping improves the steam-plant stability
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'Operation of the storage plant in the pumping improves the steam-plant stability' (Option D).
Legal Metrology • Paper-II
Power transmission lines are transposed to reduce
A)
Skin effect
B)
Ferranti effect
C)
Transmission loss
D)
Interference with neighbouring communication lines
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'Ferranti effect' (Option B).
Legal Metrology • Paper-II
Nichols chart is useful for detailed study and analysis of
A)
closed loop frequency response
B)
open loop frequency response
C)
closed loop and open loop frequency responses
D)
none of these
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'closed loop and open loop frequency responses' (Option C).
Legal Metrology • Paper-II
The steady state stability of a synchronous generator can be increased by
A)
an increase in its reactance
B)
an increase in the excitation of the machine
C)
a decrease in the moment of inertia of the machine
D)
an increase in the moment of inertia of the machine
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'an increase in the excitation of the machine' (Option B).
Legal Metrology • Paper-II
The voltage regulation of an over compound d.c. generator is always
A)
positive
B)
negative
C)
zero
D)
high
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'high' (Option D).
Legal Metrology • Paper-II
The direction of rotation of a dc shunt motor can be reversed by interchanging the
A)
supply terminals
B)
field terminals only
C)
armature terminals only
D)
none of these
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'armature terminals only' (Option C).
Legal Metrology • Paper-II
Which is the main relay for protecting up to 90% of the transmission line length in the forward direction?
A)
Directional over-current relay
B)
Mho relay
C)
Carrier current-protective relay
D)
Impedance relay
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'Carrier current-protective relay' (Option C).
Legal Metrology • Paper-II
Hysteresis and eddy current losses in electric machines depend on
A)
flux density
B)
speed
C)
speed and flux density
D)
none of these
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'speed' (Option B).
Legal Metrology • Paper-II
What is the preferred type of CB to be installed in extra high voltage ac system?
A)
Bulk oil type CB
B)
Air blast CB
C)
Vaccum CB
D)
Sulphur hexafluoride (SF6) CB
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'Air blast CB' (Option B).
Legal Metrology • Paper-II
The effect of increasing the length of air-gap in an induction motor will be to increase the
A)
power factor
B)
speed
C)
magnetizing current
D)
air-gap flux
Based on established principles in Electrical / Electronics Engineering, the correct and most appropriate choice is 'power factor' (Option A).
