BHEL Engineer Trainees Sample paper Electronics

BHEL Engineer Trainees Sample paper Electronics
BHEL engineer trainee ECE sample question paper
BHEL Engineer Trainees ET Question Paper : Electronics
1. A feedback amplifier has a closed-loop gain of —200. It should not vary more than 50%, despite 25% variation in amplifier gain A without feedback. The value of A is
(a) 800
(b) - 800
(c) 1000
(d) -1000

Ans:-D

2. A wave is propagated in a parallel-plane wave- guide. The frequency is 6GHz and plane separation is 3 cm. For the dominants mode match List I with List II and select the correct answer using the codes given below the lists:
List I
(Quantities)
A. Cut-off wave-length (cm)
B. Wave-length in wave guide (cm)
C. Phase velocity (megameter/sec.)
D. Group velocity (megameter/sec.)
List II
(Numerical values)
1. 5
3. 9.05
2. 6
4. 166
5. 543
Codes:
A B C D
(a) 1 2 5 4
(b) 2 1 4 3
(c) 2 1 5 4
(d) 5 4 2 3

Ans:-C



3. Match List-I (Device) with List-Il (Property) and select the correct answer using the codes given below the lists:
List-I
A. Planar monolithic BJT
B. Thick Film
C. Thin Film
D. Optocoupler
List - II
1. Low-cost resistors
2. Resistors suitable for high frequency use
3. Isolator
4. High frequency transistors
Codes:
A B C D
(a) 2 3 1 4
(b) 4 1 2 3
(c) 4 1 3 2
(d) 2 3 4 1

Ans:-C


4. Assuming that only the X and Y logic inputs are available and their complements X and Y are not available, what is the minimum number of two-input NAND gates required to implement X?U?
(a) 2
(b) 3
(c) 4
(d) 5

Ans:-D

5. In 8085 microprocessor, H, L register pair is used for storing
(a) Address of memory
(b) Data
(c) Address of next instruction
(d) Current instruction

Ans:-A

6. For three links in tandem, each of the first two has S/N ratio of 60 dB while the third has the same of 40 dB. The overall S/N ratio
(approx.) is
(a) 30 dB
(b) 40 dB
(c) 50 dB
(d) 60 dB

Ans:-D


7. A10 MHz carrier of peak value 10 V is amplitude modulated by a 10 kHz signal of amplitude 6V. The amplitude of each side-band frequency is
(a) 3V
(b) 4V
(c) 5V
(d) 6V

Ans:-C


8. Consider the following statements:
Delta Modulation has some significant advantage over PCM as
1. It provides greater channel capacity for a given bit-rate.
2. It does not inherently require synchronization.
3. It is more tolerant to system noise.
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



9. Consider the following statements:
Equipment is available to enable carrying more than one voice channel on
1. A pair of wires
2. A coaxial cable
3. A radio link
4. An optic fiber
Of these statements:
(a) 1, 2 and 3 are correct 4
(b) 2, 3 and 4 are correct
(c) 1 and 4 are correct
(d) 1, 2, 3 and 4 are correct

Ans:-B


10. Consider the following statements regarding noise in pulse communication systems:
1. Those forms of pulse modulation which transmit constant amplitude signals can be made to have good signal-to-noise ratio.
2. For PWM and PPM, improved signal-to- noise ratio requires higher bandwidth.
3. In PCM, the. Quantising noise goes up if the number of standard levels is increased
Of these statements:
(a) 1 and 2 are correct
(b) 1 and 3 are correct
(c) 2 and 3 are correct
(d) 1, 2 and 3 are correct

Ans:-A


11. Control of data flow within networks to ensure maximum efficiency and minimum interference between users, is achieved
(a) Through the isolation of users
(b) Through magic-T networks.
(c) By address coding
(d) By using system protocol

Ans:-C





12. Consider tie following statements:
The advantages of KU band for satellite communication are that
1. Heavy rain fall does not attenuate the signal
2. Frequencies are not shared with terrestrial microwave radio system.
3. It has a wide footprint.
4. If has smaller antennas.
Of these statements:
(a) 3 and 4 are correct
(b) 1 and 4 are correct
(c) 2 and 4 are correct
(d) 1, 3 and 4 are correct

Ans:-C


13. Match List-I (Data Comm. schemes) with List- II (Applications) and select the correct answer using the codes given below the lists:
List-I
A. Parallel synchronous
B. Parallel asynchronous
C. Serial synchronous
D. Serial asynchronous
List-II
1. Computer to computer
2. Computer to printer
3. Buses within computer
4. Telephone central office intercommunication
5. Short distance data communication
Codes:
A B C D
(a) 1 2 3 5
(b) 5 3 2 4
(c) 5 3 4 2
(d) 1 2 5 3

Ans:-A


14. The autocorrelation function of a rectangular pulse of duration T is
(a) Another rectangular pulse of duration T
(b) Another rectangular pulse of duration 2T
(c) a triangular pulse of duration T
(d) a triangular pulse of duration 2T

Ans:-D

15. The ISDN basic rate Interface specified as per CCITT standards is
(a) One B channel (64 kbps) and one D channel (16 kbps)
(b) Two B channels (64 kbps)
(c) Two B channels (64 kbps) and one D channel (16 kbps)
(d) Two B channels (64 kbps) and one D channel (64 kbps)

Ans:-C


16. Which of the following circuits need to be checked to rectify a colour TV receiver showing? No colour, monochrome picture and normal sound?
1. Colour killer
2. 3.58 sub-carrier oscillator
3. Chrome amplifier
4. Brightness control
Select the correct answer using the codes given below:
Codes:
(a) l and 2
(b) 1,2and3
(c) l, 3and4
(d) 2,3and4

Ans:-C


17. A disadvantage of CW Doppler radar is that
(a) It does not given the target Position
(b) It does not give the target velocity
(c) It requires a transponder at the target
(d) It does not give the target range

Ans:-D


18. In Decca navigation system, for a subharmonic frequency ‘f’, what is the frequency of the master station?
(a) 8f
(b) 5f
(c) 6f
(d) 7f

Ans:-B



19. In microwave communication, th4 antennas of one repeater must be accurately aligned with the next repeater in the link, because
(a) There are at least four carriers with 600-2700 channels per carrier
(b) A repeater must amplify the signal received
(c) The antenna beam widths are less than 2°
(d) The antennas are small in size

Ans:-B

Instructions: 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 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 a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

20. Assertion (A): The system with transfer function
G(s) = 10(s—12) / s(s+2) (s+3) is a minimum phase function.
Reason (R): It has a zero on the right half of the s- phase.

Ans:-D

21. Assertion (A): Data acquisition systems are widely used in a variety of industrial and scientific areas.
Reason (R): Data acquisition systems often use magnetic tape recorders.

Ans:-A


22. Assertion (A): In fiber optic communication, the 1.3 ? m, window is preferred over the 0.85 micro m window for long distance communication.
Reason (R): At 1.3 micro m, not only the attenuation of silica fiber is lower than that at 0.85 microm, the pulse broadening at the long wavelength window is also minimum.

Ans:-C

23. Assertion (A): For transmitting audio frequency signals, antennas of several hundred kilometers length would be required.
Reason (R): for efficient radiation of electromagnetic energy to occur from an antenna, the wavelength of the radiated signal must be comparable with the physical dimensions of the antenna.

Ans:-A


24. Assertion (A): In a high frequency transmission line, when a voltage is placed across the line at the sending end, the voltage and current in the line change with distance.
Reason (R): A transmission line consists of continuous conductors with a cross-sectional configuration that is constant throughout their lengths.

Ans:-A




25. Assertion (A): MOSFET RAMs are usually slower than bipolar RAMs.
Reason (R): MOSFET RAMs in comparison with bipolar RAMs can be fabricated in much larger capacity in a single IC and consume much less power.

Ans:-B