Sunday, April 15, 2012

Electrical Engineering MCQ Sample Practice Questions With Assertion Reason Type

Electrical Engineering MCQ Sample Practice Questions
Electrical Engineering Questions and Answers With Assertion Reason Type
Electrical Engineering Solved MCQ
Directions: The following 11 (eleven) items consist of two statements, one labelled the ‘Assertion A’ and the other labelled the ‘Reason R’. You are to examine these two statements and decide If the ‘Assertion A’ and the ‘Reason R’ are 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 are true and R Is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

1. Assertion (A): In dc to dc step Dow chopper, free-wheeling diode is mandatory for RL loads.
Reason (R): A part of energy fed to the RL load is dissipated in the resistance.

Ans:-B









2. Assertion (A): In the slip test for determining the d-axis and q-axis synchronous reactances ‘X d’ and ‘X q’ respectively of a salient pole machine, the stator has to be fed with suitably reduced voltage at the rated frequency and the rotor (with the field circuit open) has to be rotated at a speed slightly different from the synchronous speed, and the fluctuating terminating voltage and armature current are to be recorded for computing X d and X q
Reason (R): during the slip test, a slip frequency - voltage is induced across the open field circuit terminals that could be measured by connecting a voltmeter across these terminals.

Ans:-A


3. Assertion (A): Phase comparison pilot relaying for the protection of a transmission line is a blocking pilot.
Reason (R): The pilot signal is not required from the other end to permit tripping.

Ans:-B


4. Assertion (A): Thyristorised current source inverters do not operate at high switching frequency.
Reason (R): Thrystorised current source inverter is capable of four-quadrant operation.

Ans:-B


5. Assertion (A): A piezoelectric crystal is used for measurement of varying force only.
Reason (R) The equivalent circuit of a piezoelectric transducer has a shunt capacitor at its output.

Ans:-D


6. Assertion (A): Lag compensation permits a high gain at low frequencies.
Reason (R): Lag compensation is basically a low pass filter.

Ans:-A


7. Assertion (A): Stability is a major problem in closed loop control systems.
Reason (R): Introduction of feedback affects the location of poles of open-loop system.

Ans:-A

8. Assertion (A): The auto increment and auto decrement modes are seldom found in modern processors.
Reason (R): Using two instructions instead of one provides flexibility in implementing a pipeline.

Ans:-D


9. Assertion (A): Surface charge density is considered a physical possibility for either dielectrics or perfect conductors.
Reason (R): Surface current density is assumed only in conjunction with perfect conductors.

Ans:-B


10. Assertion (A): For continuous communication purposes, satellites are normally placed in geostationary orbit.
Reason (R): In satellite communication, uplink and downlink frequencies are different.

Ans:-B


11. Consider an SSB signal where the modulating signal is a speech signal.
Assertion (A): Its envelope detection will not recover the modulating signal.
Reason (R): The envelope of an SSB is constant.


Ans:-B

12. Consider the following statements: Phase-controlled converters
1. do not provide smooth variation of output voltage.
2. inject harmonics into the power system.
3. draw non-unity power factor (Pf) current for finite triggering angle.
Which of these statements are correct?
(a) 1, 2 and 3
(b) 1 and 2
(c) 2 and 3
(d) l and 3

Ans:-D


13. A single-phase circulating current dual converter is supplying a load. If the triggering angle of one converter is 30°, then the other converter operates at a triggering angle of
(a) 300
(b) 600
(c) 90°
(d) 150°

Ans:-D


14. The purpose of free-wheeling In a thyristor controlled ac to dc converter is to
(a) reduce the current of its associated thyristor to zero so that commutation can take place
(b) share the ‘load current of its associated thyristor
(c) conduct the load current when its associated thyristor is turned off
(d) maintain voltage across load at constant value

Ans:-C


15. Opto couplers are used In transistor base drive circuit for
(a) amplification of base drive signal
(b) isolation between control and power circuits
(c) fast switching of power transistor
(d) protection against over current

Ans:-C


15. Given that N is the actual number of instructions executed and CPI is the average number of cycles per instruction, then
(a) both CISE (Complex instruction set computer) and RISE (Reduced instruction set computer) processors aim to reduce N at the expense of CPI
(b) CISE processors aim to reduce N at the expense of CPI whereas RISC processors aim to reduce CPI at the expense of N
(c) RISC processors aim to reduce N at the expense of CPI whereas CISC processor aim to reduce CPI at the expense of N
(d) both CISC and RISC processors aim to reduce CPI at the expense of N

Ans:-B

16. Considers the following statements:
As compared to Si single crystal grown by the
CZ method, the Si single crystal grown by the
FZ method should have
1. lesser oxygen contamination.
2. uniforms doping throughout length of the crystal.
3. more substitutional carbon atoms in the crystal
When of these statements are correct?
(a) 1, 2 and 3
(b) 1 and 3
(c) 2 and 3
(d) l and 2

Ans:-B



17. If a 3-phasor induction motor and a 1-phase induction motor of the same kW rating and same winding voltage are compared, then
(a) both will be of same size and efficiency
(b) the 3-phase induction motor will be bigger in size and less efficient
(c) the 3-phase induction motor will be smaller in size and more efficient
(d) the 3-phase induction motor will be bigger in size and more efficient

Ans:-C


18. In the slip power recovery method of speed control of a 3-phase wound rotor induction motor, to operate it in the subsynchronous region of speed, a voltage has to be injected across the rotor terminals
(a) in phase with the rotor induced emf
(b) in phase opposition to the rotor induced emf
(c) leading the rotor induced emf by 90°
(d) lagging the rotor induced emf by 90°

Ans:-C

19. Two transformers X and Y with Identical ratings and dimensions have 0.8mm and 1.2 mm thick laminations respectively. If R m and X m are the magnetizing branch parameters in the equivalent
circuit, then
(a) R m values in both are likely to be equal, but X m of X is likely to be higher than X of Y
(b) X m values in both are likely to be equal, but R m of X is likely to be higher than R m of Y
(c) X m values in both are likely to be equal, but R m of X is likely to be lower than R m of Y
(d) R m values in both are likely to be equal, but X m of X is likely to be lower than X m of Y

Ans:-D





20. Consider the following statements in respect of important features of IGBT:
1. It has a high impedance gate as that of a MOSFET.
2. It has a low ON state voltage as that of a BJT.
3. It can block negative voltages as in the case of GTO.
Which of these statements are correct?
(a) l and 2
(b) l and 3
(c) 2 and 3
(d) 1, 2 and 3

Ans:-D

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