electrical engineering MCQ Test
Engg Multiple Choice Questions
Electrical Engineering objective questions MCQ for graduate Engineer
1. The frequency of an LC circuit of a tuned base- tuned emitter type of coupled oscillator having resonant frequency of crystal as a is
(a) slightly less than ω
(b) equal to ω
(c) slightly more than ω
(d) at least 2 ω
Ans:-A
2. In an operational amplifier the bandwidth (B) in terms of rise time (t) is given ’by’
(a) 0.35 / tr
(b) 1 / 0.35 tr
(c) 0.35 tr
(d) tr / 0.35
Ans:-B
3. The figure of merit of a logic family is given by the product of
(a) gain and bandwidth
(b) propagation delay time and power dissipation
(c) fanout and propagation delay time
(d) noise margin and power dissipation
Ans:-A
4. Match List I with List II and select the correct answer using the codes given below the lists: List I
(Boolean statements is true)
A. AØB=O
B. A+B=O
C. A .B=O
D. AØB=l
List II
(Conditions under which)
1. A≠B
2. A=B
3. A=l and B=l
4. A=l and B=O
Codes:
A B C D
(a) 1 2 4 3
(b) 2 3 4 1
(c) 1 3 2 4
(d) 2 4 1 3
Ans:-C
5. For an energy signal g(t) and its time-shifted version g (t- r), the
(a) amplitude spectra are identical and their phase spectra are also identical
(b) amplitude spectra are identical but their phase spectra are different
(c) amplitude spectra are different but their phase spectra are identical
(d) amplitude spectra are different and their phase spectra are also different
Ans:-B
6. If the number of bits in a PCM system is increased from ii to rn+ 1, the signal-to-quanhisation noise ratio will increase by a factor
(a) (n+1) / n
(b) (n+1)2/n2
(c) 2
(d) 4
Ans:-B
7. A 600 Hz signal is sampled at a rate of 1000 samples per second. The frequency components of sampled signal will consist of
(a) 400 Hz and 600 Hz
(b) 400 Hz, 600 Hz and 1200 Hz.
(c) 600 Hz, 800 Hz, 1000 Hz and. 1200 Hz
(d) 600 Hz, 1000 Hz, 1200 Hz and 1400 Hz
Ans:-A
8. Consider the following statements regarding colour television:
1. Only chrominance signals occupy the full bandwidth.
2. Only luminance signals occupy the full bandwidth.
3. All the three signals occupy the full bandwidth.
4. The bandwidths of both the chrominance signals are equal
5. The bandwidth of luminance signals is smaller than that of the chrominance signals.
Of these statements:
(a) 1 and 4 are correct
(b) 2 alone is correct
(c) 3 and 4 are correct
(d) 5 alone is correct
Ans:-A
9. Instrument Leading System (ILS) and Ground Controlled Approach (GCA) are aircraft landing systems, wherein
(a) both use radar units on the ground
(b) both use special receivers on board the aircraft
(c) ILS uses special receivers in the aircraft and GCA uses radar units on the ground
(d) ILS uses radar units on the ground and GCA uses special receivers on the ground
Ans:-D
10. The standard test tone for audio portion of CCIR circuits is
(a) 0 d B m at 1000 Hz
(b) —3OdBmat800Hz
(c) 0 d B m at 400 Hz
(d) —3OdBmat400Hz
Ans:-A
11. In dc machine, the field system has to be provided on stator unlike synchronous machines wherein it could be on any member, because
(a) it reduces field structure iron losses
(b) it gives more uniform air-gap flux distribution
(c) commentator action is not possible otherwise
(d) dc machines are comparatively low rating machines
Ans:-D
12. In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation
Now, if the brushes are given a lead of 90° (electrical), then the MNA will
(a) shift forward by 90°
(b) shift forward by more than 90°
(c) shift forward by less than 90
(d) coincide with the GNA
Ans:-D
13. A cumulatively compounded dc motor runs at 1000 rpm at no-load. On full load, the flux increases by 10%, whereas the full load drop in the combined resistance of the armature and series field is 5% Neglecting magnetic saturation, the full load speed will be nearly
(a) 863 rpm
(b) 909 rpm
(c) 1000rpm
(d) 1050rpm
Ans:-C
14. A dc over compound generator is supplying power to an infinite bus. If the prime mover is accidentally cut off, the dc machine will
(a) stop running
(b) run as cumulatively compounded motor in reverse direction
(c) run as differentially compounded motor in reverse direction
(d) run as differentially compounded motor in same direction
Ans:-C
15. Match List I with List II and select the correct answer using the codes given below the lists:
List I
(Load pf)
A. Zero leading
B. Unity
C. Zero lagging
D. Zero with armature terminals suddenly short-circuited
List II
(Nature of armature flux in an alternator)
1. Demagnetising
2. Magnetising
3. Cross magnetizing
4. Initially constant, demagnetizing
Codes:
A B C D
(a) 1 2 4 3
(b) 2 3 1 4
(c) 4 3 1 2
(d) 2 1 3 4
Ans:-B
16. A dc shunt motor is run under the following conditions:
1. Normal voltage with no additional resistance in armature or field circuits.
2. 50% normal voltage with no additional resistance in armature or field circuits.
3. Normal voltage with a small external resistance in the armature circuit of a value equal to the armature resistance.
4. Normal speed of the motor would increase in the sequence
(a) 1,2,3,4
(b) 1,4,3,2
(c) 2,1,4,3
(d) 2,3,1,4
Ans:-B
17. Consider the following statements about a three- phase synchronous generator synchronized to an infinite bus when its mechanical input is increased gradually with field current held constant:
1. The power factor of the current supplied becomes more lagging.
2. The power factor of the current supplied improves.
3. The power factor remains unity.
4. The load angle is increased.
Of these statements:
(a) 1 alone is correct
(b) 2 alone is correct
(c) 2 and 4 are correct
(d) 3 and 4 are correct
Ans:-A
18. Which of the following will change in a three- phase synchronous motor, as a consequence of excitation variations?
1. Pull-out torque
2. Torque angle
3. Magnitude and power factor of stator current
4. Output power
Select the correct answer using the codes given below:
Codes:
(a) l and 3
(b) 2 and 4
(c) 2,3 and 4
(d) 1, 2 and 3
Ans:-B
19. Following a sudden short-circuit at the terminals of a 3-phase unloaded synchronous generator, the initial effect of the pole-face damper winding, is to
(a) establish the armature flux through the direct-axis magnetic circuit of the machine
(b) allow only partial linkage of the armature flux with the main field winding
(c) confine the armature flux to completely link the damper winding
(d) Repel the armature flux and confine it to the leakage flux path in the air-gap.
Ans:-C
20. Consider the following statements about single- phase reluctance motor:
1. The starting torque is a function of rotor position.
2. The torque developed at sub synchronous speeds varies sinusoidally.
3. Starting is asynchronous but running is synchronous.
4. It pulls synchronism on switching on dc excitation.
Of these statements:
(a) 1, 2 and 3 are correct
(b) 1, 3 and 4 are correct
(c) 2, 3 and 4 are correct
(d) 1 and 4 are correct
Ans:-D
Showing posts with label Electrical. Show all posts
Showing posts with label Electrical. Show all posts
Sunday, July 31, 2011
electrical engineering solved question paper
electrical engineering solved question paper
electrical engineering Solved Question Papers
1. If the aperture of the radar antenna is doubled, then the radar range will increase by a factor of
(a)√2
(b) 2
(c) 4
(d) 16
Ans:-A
2. Match List I with List II and select the correct answer using the codes given below the lists:
List I
(Systems)
A. Satellite Communication
B. Line Carrier Telephony
C. Monophonic Broadcasting
D. Stereophonic Broadcasting
List II
(Modulation)
1. SSB
2. AM
3. SQPSKJOQPSK
4. FM
5. PM
Codes:
A B C D
(a) 3 4 1 2
(b) 1 3 5 2
(c) 2 5 1 3
(d) 3 1 2 4
Ans:-D
3. Consider the following types of machines:
1. 2-phase A. C servomotor
2. Conventional 2-phase induction motor
3. Stepper motor
4. Tacho generator
The rotors are generally of drag cup construction in the case of
(a) l, 2 and 4
(b) l and 3
(c) 3 and 4
(d) l and 4
Ans:-D
4. Consider the following statements regarding the effect of adding a pole in the open-loop transfer function on the closed-loop step response:
1. It decreases the maximum overshoot.
2. It increases the rise lime.
3. It reduces the ‘bandwidth.
Of these statements:
(a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 3 are correct
(d) 1 and 3 are correct
Ans:-B
5. The first two rows of Routh’s tabulation of a fourth-order system are:
S4 1 10 5
S5 2 20
The number of roots of the system lying on the right half of s-plane is
(a) Zero
(b) 2
(c) 3
(d) 4
Ans:-C
6. A control system whose step response is —0.5 (1+ e-2t ) is cascaded to another control block whose impulse response is e-4. The transfer function of the cascaded combination is
(a) 1 / (s + 1) (s + 2)
(b) 1 / s(s+1)
(c) 1 / s(s+2)
(d) 0.5 / (s+1)(s+2)
Ans:-B
7. The error response of a second order system to a step input is obtained as
E(t) = 1.66 e-8t sin (6t + 37°) The damping ratio is
(a) 0.4
(b) 0.5
(c) 0.8
(d) 1.0
Ans:-D
8. In a linear system, an input of 5 sin ω t produces an output of 10 cos ω t. The output corresponding to input 10 cost wt will be equal to
(a) +5 sin ω t
(b) —5 sin ω t
(c) +20 sin ω t
(d) 20 sin ω t
Ans:-C
9. The resistances 100 Ω ± 5 Ω and ± 15 Ω are connected in series. If the errors are spec Wed as standard deviations, the resultant error will be
(a) ±10 Ω
(b) ±10.6 Ω
(c) ±.15.8Ω
(d) ±20 Ω
Ans:-A
10. Match List I with List II and select the correct answer using the codes given below the lists:
List I
(Parameter measured)
A. Audio frequency
B. High Q inductor
C. Dielectric loss
D. Low Q inductor
List II
(Bridge)
1. Maxwell bridge
2. Hay bridge
3. Wien bridge
4. Schering bridge
Codes:
A B C D
(a) 3 4 2 1
(b) 3 2 4 1
(c) 4 2 1 3
(d) 1 4 2 3
Ans:-A
11.. A sinusoidal waveform, when observed on an oscilloscope has peak to peak amplitude of 6 cm. If the vertical sensitivity setting c 5 V/cm, the rms value of the voltage is
(a) 10.6 V
(b) 11.1 V
(c) 12.6V
(d) 15 V
Ans:-A
12. In the two-wattmeter method of measuring power in a balanced three-phase circuit, one wattmeter shows zero and the other positive maximum. The load power factor is
(a) zero
(b) 0.5
(c) 0.866
(d) 1.0
Ans:-B
13. A 35 V dc supply is connected across a resistance of 600 in series with an unknown resistance Rx A voltmeter having a resistance of 1.2 k Ω is connected across 600Ω resistance and reads 5 V. The value of resistance Rx will be
(a) 120Ω
(b) 400Ω
(c) 1.8 Ω
(d) 2.4Ω
Ans:-A
14. ‘Creep’ in energy meters can be prevented by
(a) using extra turns of the voltage coil
(b) having two holes on opposite sides of the disc
(c) using a stronger brake magnet
(d) using steel laminations of high permeability
Ans:-D
15. An integrating digital voltmeter measures
(a) true average value
(b) rms value
(c) peak value
(d) peak to peak value
Ans:-A
16. A frequency modulation wave is passed through
1. harmonic generator
2. frequency translator
The modulation index is
(a) not changed in either case
(b) changed only in1
(c) changed only in 2
(d) changed in both 1 and 2
Ans:-B
17. For high speed operation which of the folio wing parameters may have to be minimized?
1. Junction capacitance
2. Dynamic forward resistance
3. Depletion layer thickness
4. Charge storage
Choose the correct set of parameters using the codes giving below:
Codes:
(a) l and 2
(b) 1, 2 and 3
(c) l and 4
(d) 2, 3 and 4
Ans:-D
18. A MOSFET having gate-source and gate-drain capacitances as Cgs, and Cgd respectively Is connected as a CS amplifier having voltage gain = -Av The input capacitance for this amplifier is
(a) Cgs + Cgd
(b) Cgs + (l+AV) CSd
(c) Cgs (1 + Av) + Cgd
(d) Cgs — Cgd
Ans:-B
19. An R-C coupled transistor amplifier has a lower 3-dB frequency of 100 Hz due .to coupling capacitor. The emitter bypass capacitor is of such a value that the lower 3-dB frequency due to emitter degeneration alone is also 100 Hz. The lower 3-dB frequency of the stage will be
(a) 64 Hz
(b) 100 Hz
(c) 156 Hz
(d) 244 Hz
Ans:-C
20. A class B push-pull transistor amplifier is operated under optimum conditions. Vcc = 30 V, Audio Power = 4.5 watts. With the usual simplifying assumptions
(a) the DC power drawn from Vcc is 9 watts
(b) the power dissipated by each transistor is 2.25 watts
(c) the reflected resistance in the primary of the transformer is 200 ohms
(d) the peak ac collector current is 0.3 amps
Ans:-B
electrical engineering Solved Question Papers
1. If the aperture of the radar antenna is doubled, then the radar range will increase by a factor of
(a)√2
(b) 2
(c) 4
(d) 16
Ans:-A
2. Match List I with List II and select the correct answer using the codes given below the lists:
List I
(Systems)
A. Satellite Communication
B. Line Carrier Telephony
C. Monophonic Broadcasting
D. Stereophonic Broadcasting
List II
(Modulation)
1. SSB
2. AM
3. SQPSKJOQPSK
4. FM
5. PM
Codes:
A B C D
(a) 3 4 1 2
(b) 1 3 5 2
(c) 2 5 1 3
(d) 3 1 2 4
Ans:-D
3. Consider the following types of machines:
1. 2-phase A. C servomotor
2. Conventional 2-phase induction motor
3. Stepper motor
4. Tacho generator
The rotors are generally of drag cup construction in the case of
(a) l, 2 and 4
(b) l and 3
(c) 3 and 4
(d) l and 4
Ans:-D
4. Consider the following statements regarding the effect of adding a pole in the open-loop transfer function on the closed-loop step response:
1. It decreases the maximum overshoot.
2. It increases the rise lime.
3. It reduces the ‘bandwidth.
Of these statements:
(a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 3 are correct
(d) 1 and 3 are correct
Ans:-B
5. The first two rows of Routh’s tabulation of a fourth-order system are:
S4 1 10 5
S5 2 20
The number of roots of the system lying on the right half of s-plane is
(a) Zero
(b) 2
(c) 3
(d) 4
Ans:-C
6. A control system whose step response is —0.5 (1+ e-2t ) is cascaded to another control block whose impulse response is e-4. The transfer function of the cascaded combination is
(a) 1 / (s + 1) (s + 2)
(b) 1 / s(s+1)
(c) 1 / s(s+2)
(d) 0.5 / (s+1)(s+2)
Ans:-B
7. The error response of a second order system to a step input is obtained as
E(t) = 1.66 e-8t sin (6t + 37°) The damping ratio is
(a) 0.4
(b) 0.5
(c) 0.8
(d) 1.0
Ans:-D
8. In a linear system, an input of 5 sin ω t produces an output of 10 cos ω t. The output corresponding to input 10 cost wt will be equal to
(a) +5 sin ω t
(b) —5 sin ω t
(c) +20 sin ω t
(d) 20 sin ω t
Ans:-C
9. The resistances 100 Ω ± 5 Ω and ± 15 Ω are connected in series. If the errors are spec Wed as standard deviations, the resultant error will be
(a) ±10 Ω
(b) ±10.6 Ω
(c) ±.15.8Ω
(d) ±20 Ω
Ans:-A
10. Match List I with List II and select the correct answer using the codes given below the lists:
List I
(Parameter measured)
A. Audio frequency
B. High Q inductor
C. Dielectric loss
D. Low Q inductor
List II
(Bridge)
1. Maxwell bridge
2. Hay bridge
3. Wien bridge
4. Schering bridge
Codes:
A B C D
(a) 3 4 2 1
(b) 3 2 4 1
(c) 4 2 1 3
(d) 1 4 2 3
Ans:-A
11.. A sinusoidal waveform, when observed on an oscilloscope has peak to peak amplitude of 6 cm. If the vertical sensitivity setting c 5 V/cm, the rms value of the voltage is
(a) 10.6 V
(b) 11.1 V
(c) 12.6V
(d) 15 V
Ans:-A
12. In the two-wattmeter method of measuring power in a balanced three-phase circuit, one wattmeter shows zero and the other positive maximum. The load power factor is
(a) zero
(b) 0.5
(c) 0.866
(d) 1.0
Ans:-B
13. A 35 V dc supply is connected across a resistance of 600 in series with an unknown resistance Rx A voltmeter having a resistance of 1.2 k Ω is connected across 600Ω resistance and reads 5 V. The value of resistance Rx will be
(a) 120Ω
(b) 400Ω
(c) 1.8 Ω
(d) 2.4Ω
Ans:-A
14. ‘Creep’ in energy meters can be prevented by
(a) using extra turns of the voltage coil
(b) having two holes on opposite sides of the disc
(c) using a stronger brake magnet
(d) using steel laminations of high permeability
Ans:-D
15. An integrating digital voltmeter measures
(a) true average value
(b) rms value
(c) peak value
(d) peak to peak value
Ans:-A
16. A frequency modulation wave is passed through
1. harmonic generator
2. frequency translator
The modulation index is
(a) not changed in either case
(b) changed only in1
(c) changed only in 2
(d) changed in both 1 and 2
Ans:-B
17. For high speed operation which of the folio wing parameters may have to be minimized?
1. Junction capacitance
2. Dynamic forward resistance
3. Depletion layer thickness
4. Charge storage
Choose the correct set of parameters using the codes giving below:
Codes:
(a) l and 2
(b) 1, 2 and 3
(c) l and 4
(d) 2, 3 and 4
Ans:-D
18. A MOSFET having gate-source and gate-drain capacitances as Cgs, and Cgd respectively Is connected as a CS amplifier having voltage gain = -Av The input capacitance for this amplifier is
(a) Cgs + Cgd
(b) Cgs + (l+AV) CSd
(c) Cgs (1 + Av) + Cgd
(d) Cgs — Cgd
Ans:-B
19. An R-C coupled transistor amplifier has a lower 3-dB frequency of 100 Hz due .to coupling capacitor. The emitter bypass capacitor is of such a value that the lower 3-dB frequency due to emitter degeneration alone is also 100 Hz. The lower 3-dB frequency of the stage will be
(a) 64 Hz
(b) 100 Hz
(c) 156 Hz
(d) 244 Hz
Ans:-C
20. A class B push-pull transistor amplifier is operated under optimum conditions. Vcc = 30 V, Audio Power = 4.5 watts. With the usual simplifying assumptions
(a) the DC power drawn from Vcc is 9 watts
(b) the power dissipated by each transistor is 2.25 watts
(c) the reflected resistance in the primary of the transformer is 200 ohms
(d) the peak ac collector current is 0.3 amps
Ans:-B
Thursday, July 28, 2011
Objective electrical engineering solved question papers
Objective electrical engineering solved question papers
Electrical Engineering objective questions MCQ
Electrical Engineering Solved Sample Questions
1. A single-phase induction on motor with only the main winding excited would produce zero torque at
(a) synchronous speed only
(b) starting and synchronous speed
(c) starting only
(d) starting and a speed slightly below synchronous speed
Ans:-B
2. A polyphase slip-ring induction machine has the stator and rotor windings wound for
(a) the same number of phase 6ut different number of pairs of poles
(b) the same number of pairs of poles but different number of phases
(c) the same number of phases with number of pairs of poles either equal or different
(d) the same number of pairs of poles with number of phases either equal or different
Ans:-D
3. The single-phase Induction motor is started with
(a) capacitance connection
(b) inductance connection
(c) resistance connection
(d) shaded pole arrangement
Ans:-A
4. Low voltage starting of induction motors is prescribed because
(a) high starting current at full voltage would damage the windings
(b) it facilitates smooth acceleration.
(c) it increases the life of the motor.
(d) it is mandated by electric supply authorities to prevent voltage dips at other consumer premises.
Ans:-A
5. The leakage flux in a transformer depends upon the
(a) applied voltage
(b) frequency
(c) load current
(d) mutual flux
Ans:-C
6. The voltage regulation of a large transformer is mainly influenced by
(a) no-load current and load power factor
(b) winding resistances and load power factor
(c) leakage fluxes and load power factor
(d) winding resistances and core loss
Ans:-C
7. The following lists relate to speed control of dc motors. Match List I with List II, and select the correct answer using the codes given below the lists:
List I
A. Armature voltage control
B. Field current control
C. Use of diverter resistance
D. Rheostatic control
List II
1. Speeds above base speed
2. Speeds below base speed
3. Poor motor efficiency
4. Speed control of series motor
Codes:
A B C D
(a) 1 2 3 4
(b) 2 1 4 3
(c) 4 1 3 2
(d) 2 3 1 4
Ans:-B
8. In a line printer used to print the output of a computer, the paper is required to be advanced by line spacing as soon as printing of the line is over. Which one of the following motors is best suited for this application?
(a) DC motor
(b) Synchronous motor
(c) Induction motor
(d) Stepper motor
Ans:-D
9. While plugging a 3-phase Induction motor, one supply terminal gets disconnected, then the motor will
(a) Continue to run in the same direction
(b) stop
(c) start rotating in the opposite direction at the same speed
(d) start rotating in the opposite direction at reduced speed
Ans:-A
10. The inductance of a three-phase transmission line is 1.2 mH /phase/km. If the spacing of conductors and the radius of the conductor are doubled, then the Inductance of Ike line will be
(a) 4.8 mH /phase/km
(b) 1.2 mH /phase/km
(c) (In 2) x 1.2 mH /phase/km
(d) (In 4) x 1.2 mH /phase/km
Ans:-B
11. A three-phase transmission line of negligible resistance and capacitance has an inductive reactance of 100 ohms per phase. When the sending-end and receiving-end voltages are maintained at 110 kV, the maximum power that can be transmitted will be
(a) 121MW
(b) 121/3 MW
(c) 363 MW
(d) 363 kW
Ans:-A
12. The surge impedance of a 100 km long underground cable is 50 ohms. The surge impedance of a 40 km long similar cable would be
(a) 20 ohms
(b) 50 ohms
(c) 80 ohms
(d) 125 ohms
Ans:-B
13. A string insulator has 4 units. The voltage across the bottom-most unit is 33.33% of the total voltage. Its string efficiency is
(a) 25%
(b) 33.33%
(c) 66.67%
(d) 75%
Ans:-D
14. The design of insulation for systems above 400 kV, is based upon
(a) lightning over voltage
(b) switching surges
(c) system voltage level
(d) system load level
Ans:-B
15. Bundled conductors in EHV transmission systems provide
(a) increased line reactance
(b) reduced line capacitance
(c) reduced voltage gradient
(d) increased corona loss
Ans:-C
16. A power system is subjected to a fault which makes the zero sequence component of current equal to zero. The nature of fault is
(a) double line to ground fault
(b) double line fault
(c) line of ground fault
(d) three-phase to ground fault
Ans:-B
17. For which of the following reasons is a differential relay biased to avoid maloperation when used for transformer protection?
(a) Saturation of CT’s
(b) Mismatch to CT ratios
(c) Difference in connection of both sides
(d) Current setting multiplier
Select the correct answer using the codes given below:
Codes:
(a) l and 4
(b) l and 2
(c) 2, 3 and 4
(d) 1, 2 and 3
Ans:-D
18. Protection scheme used for detection of loss of excitation of a very large generating unit feeding power into a grid employs
(a) under voltage relay
(b) offset mho relay
(c) under frequency relay
(d) percentage differential relay
Ans:-B
19. Which one of the following is not true regarding HVDC transmission?
(a) Corona loss is much more in HVDC transmission.
(b) The power transmission capability of bipolar line is almost the same as that of signal circuit ac line
(c) HVDC link can operate between two ac systems whose frequencies need not be equal
(d) There is no distance limitation for HVDC transmission by underground cable
Ans:-A
Directions: The following items consist of two statements, one labelled the ‘Assertion A’ and the other labelled the ‘Reason R’. You are to examine these two statements carefully and decide if the Assertion A and the Reason R is individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answer to these items using the codes given below and mark your answer sheet accordingly.
Codes:
(a) Both A and R is true and R is the correct explanation of A
(b) Both A and R is true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
20. Assertion (A) : In three-phase star connected network, the neutral point can assume any potential upto phase voltage.
Reason (R) : The three-phase voltage system is unbalanced. The three voltages are not equal in magnitude but they are displaced by 1200.
Ans:-A
21. Assertion (A) : In a balanced three-phase star connected system, the line voltage is equal to 1.732 times the phase voltage.
Reason (R) : The line voltage is the vector sum of the two phase voltages.
Ans:-C
22. Assertion (A): Linearity is essential for the servo amplifiers.
Reason (R) : The servo amplifiers are used to amplify’ the output of the null detector.
Ans:-B
23. Assertion (A): The sampling period of a sampled data system must be ≤ 0.5 s to have a bandwidth ≤ 6.28 rad/s.
Reason (R): The signal is fully preserved in the sampled version so long as the sampling frequency is at least twice the maximum frequency contained in the signal.
Ans:-A
24. Assertion (A): For High-Q coils, inductance measurement is better done with Hay’s Bridge rather than with Maxwell’s Bridge.
Reason (R): Hay’s Bridge uses the standard capacitor in series with a variable resistor while Maxwell’s Bridge uses it in parallel.
Ans:-A
25. Assertion (A): Self-biasing method of biasing is generally used for a CE amplifier. Reason (R): The design of self-biasing circuit is very easy as compared to other biasing circuits.
Ans:-A
26. Assertion (A): In analog computation only summing amplifiers and integrators are used.
Reason (R): The differentiators using operational amplifiers cannot be designed.
Ans:-A
27. Assertion (A): In a salient pole 3-phase alternator, direct axis synchronous reactance is more than the quadrature axis synchronous reactance.
Reason (R): The length of air-gap along the direct axis of the salient pole 3-phase alternator is less than that along quadrature axis.
Ans:-A
28. Assertion (A): Adaptive delta modulation circuit has less distortion.
Reason (R): Quantisation noise is reduced.
Ans:-A
29. Assertion (A): A phase controlled line commutated converter can be operated both as rectifier and invertors.
Reason (R): S.C.R.’s have the property of blocking positive as well as negative voltages and they can be made conducting whenever required during the positive half cycle.
Ans:-C
30. Assertion (A) : In the nominal — π model of an overhead transmission line, the value of the sending-end voltage obtained for the normal rated load at the receiving-end at rated voltage, is higher than the actual value.
Reason (R): The nominal — π method underemphasize the effect of line capacitance giving a higher value of the sending-end voltage than the actual.
Ans:-C
Electrical Engineering objective questions MCQ
Electrical Engineering Solved Sample Questions
1. A single-phase induction on motor with only the main winding excited would produce zero torque at
(a) synchronous speed only
(b) starting and synchronous speed
(c) starting only
(d) starting and a speed slightly below synchronous speed
Ans:-B
2. A polyphase slip-ring induction machine has the stator and rotor windings wound for
(a) the same number of phase 6ut different number of pairs of poles
(b) the same number of pairs of poles but different number of phases
(c) the same number of phases with number of pairs of poles either equal or different
(d) the same number of pairs of poles with number of phases either equal or different
Ans:-D
3. The single-phase Induction motor is started with
(a) capacitance connection
(b) inductance connection
(c) resistance connection
(d) shaded pole arrangement
Ans:-A
4. Low voltage starting of induction motors is prescribed because
(a) high starting current at full voltage would damage the windings
(b) it facilitates smooth acceleration.
(c) it increases the life of the motor.
(d) it is mandated by electric supply authorities to prevent voltage dips at other consumer premises.
Ans:-A
5. The leakage flux in a transformer depends upon the
(a) applied voltage
(b) frequency
(c) load current
(d) mutual flux
Ans:-C
6. The voltage regulation of a large transformer is mainly influenced by
(a) no-load current and load power factor
(b) winding resistances and load power factor
(c) leakage fluxes and load power factor
(d) winding resistances and core loss
Ans:-C
7. The following lists relate to speed control of dc motors. Match List I with List II, and select the correct answer using the codes given below the lists:
List I
A. Armature voltage control
B. Field current control
C. Use of diverter resistance
D. Rheostatic control
List II
1. Speeds above base speed
2. Speeds below base speed
3. Poor motor efficiency
4. Speed control of series motor
Codes:
A B C D
(a) 1 2 3 4
(b) 2 1 4 3
(c) 4 1 3 2
(d) 2 3 1 4
Ans:-B
8. In a line printer used to print the output of a computer, the paper is required to be advanced by line spacing as soon as printing of the line is over. Which one of the following motors is best suited for this application?
(a) DC motor
(b) Synchronous motor
(c) Induction motor
(d) Stepper motor
Ans:-D
9. While plugging a 3-phase Induction motor, one supply terminal gets disconnected, then the motor will
(a) Continue to run in the same direction
(b) stop
(c) start rotating in the opposite direction at the same speed
(d) start rotating in the opposite direction at reduced speed
Ans:-A
10. The inductance of a three-phase transmission line is 1.2 mH /phase/km. If the spacing of conductors and the radius of the conductor are doubled, then the Inductance of Ike line will be
(a) 4.8 mH /phase/km
(b) 1.2 mH /phase/km
(c) (In 2) x 1.2 mH /phase/km
(d) (In 4) x 1.2 mH /phase/km
Ans:-B
11. A three-phase transmission line of negligible resistance and capacitance has an inductive reactance of 100 ohms per phase. When the sending-end and receiving-end voltages are maintained at 110 kV, the maximum power that can be transmitted will be
(a) 121MW
(b) 121/3 MW
(c) 363 MW
(d) 363 kW
Ans:-A
12. The surge impedance of a 100 km long underground cable is 50 ohms. The surge impedance of a 40 km long similar cable would be
(a) 20 ohms
(b) 50 ohms
(c) 80 ohms
(d) 125 ohms
Ans:-B
13. A string insulator has 4 units. The voltage across the bottom-most unit is 33.33% of the total voltage. Its string efficiency is
(a) 25%
(b) 33.33%
(c) 66.67%
(d) 75%
Ans:-D
14. The design of insulation for systems above 400 kV, is based upon
(a) lightning over voltage
(b) switching surges
(c) system voltage level
(d) system load level
Ans:-B
15. Bundled conductors in EHV transmission systems provide
(a) increased line reactance
(b) reduced line capacitance
(c) reduced voltage gradient
(d) increased corona loss
Ans:-C
16. A power system is subjected to a fault which makes the zero sequence component of current equal to zero. The nature of fault is
(a) double line to ground fault
(b) double line fault
(c) line of ground fault
(d) three-phase to ground fault
Ans:-B
17. For which of the following reasons is a differential relay biased to avoid maloperation when used for transformer protection?
(a) Saturation of CT’s
(b) Mismatch to CT ratios
(c) Difference in connection of both sides
(d) Current setting multiplier
Select the correct answer using the codes given below:
Codes:
(a) l and 4
(b) l and 2
(c) 2, 3 and 4
(d) 1, 2 and 3
Ans:-D
18. Protection scheme used for detection of loss of excitation of a very large generating unit feeding power into a grid employs
(a) under voltage relay
(b) offset mho relay
(c) under frequency relay
(d) percentage differential relay
Ans:-B
19. Which one of the following is not true regarding HVDC transmission?
(a) Corona loss is much more in HVDC transmission.
(b) The power transmission capability of bipolar line is almost the same as that of signal circuit ac line
(c) HVDC link can operate between two ac systems whose frequencies need not be equal
(d) There is no distance limitation for HVDC transmission by underground cable
Ans:-A
Directions: The following items consist of two statements, one labelled the ‘Assertion A’ and the other labelled the ‘Reason R’. You are to examine these two statements carefully and decide if the Assertion A and the Reason R is individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answer to these items using the codes given below and mark your answer sheet accordingly.
Codes:
(a) Both A and R is true and R is the correct explanation of A
(b) Both A and R is true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
20. Assertion (A) : In three-phase star connected network, the neutral point can assume any potential upto phase voltage.
Reason (R) : The three-phase voltage system is unbalanced. The three voltages are not equal in magnitude but they are displaced by 1200.
Ans:-A
21. Assertion (A) : In a balanced three-phase star connected system, the line voltage is equal to 1.732 times the phase voltage.
Reason (R) : The line voltage is the vector sum of the two phase voltages.
Ans:-C
22. Assertion (A): Linearity is essential for the servo amplifiers.
Reason (R) : The servo amplifiers are used to amplify’ the output of the null detector.
Ans:-B
23. Assertion (A): The sampling period of a sampled data system must be ≤ 0.5 s to have a bandwidth ≤ 6.28 rad/s.
Reason (R): The signal is fully preserved in the sampled version so long as the sampling frequency is at least twice the maximum frequency contained in the signal.
Ans:-A
24. Assertion (A): For High-Q coils, inductance measurement is better done with Hay’s Bridge rather than with Maxwell’s Bridge.
Reason (R): Hay’s Bridge uses the standard capacitor in series with a variable resistor while Maxwell’s Bridge uses it in parallel.
Ans:-A
25. Assertion (A): Self-biasing method of biasing is generally used for a CE amplifier. Reason (R): The design of self-biasing circuit is very easy as compared to other biasing circuits.
Ans:-A
26. Assertion (A): In analog computation only summing amplifiers and integrators are used.
Reason (R): The differentiators using operational amplifiers cannot be designed.
Ans:-A
27. Assertion (A): In a salient pole 3-phase alternator, direct axis synchronous reactance is more than the quadrature axis synchronous reactance.
Reason (R): The length of air-gap along the direct axis of the salient pole 3-phase alternator is less than that along quadrature axis.
Ans:-A
28. Assertion (A): Adaptive delta modulation circuit has less distortion.
Reason (R): Quantisation noise is reduced.
Ans:-A
29. Assertion (A): A phase controlled line commutated converter can be operated both as rectifier and invertors.
Reason (R): S.C.R.’s have the property of blocking positive as well as negative voltages and they can be made conducting whenever required during the positive half cycle.
Ans:-C
30. Assertion (A) : In the nominal — π model of an overhead transmission line, the value of the sending-end voltage obtained for the normal rated load at the receiving-end at rated voltage, is higher than the actual value.
Reason (R): The nominal — π method underemphasize the effect of line capacitance giving a higher value of the sending-end voltage than the actual.
Ans:-C
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