BHEL Engineer Trainees Sample paper Electronics

BHEL Engineer Trainees Sample paper Electronics
BHEL engineer trainee model question paper of electronics
BHEL Question Paper Answer free Sample Paper

1. IC 74121 TTL one shot IC is used without connecting any external capacitor between Cext, and Rext / pin. The Rint pin is connected to Vcc On triggering, one would expect
(a) No output pulse
(b) An output pulse of duration of the order of seconds
(c) An output pulse of variable duration
(d) an output pulse of duration of the order of 30-35 nanoseconds

Ans:-C

2. An npn transistor connected as -a common emitter switch has ICBO = 1 ? A and h FE = 100. The OFF state current of this switch is of the order of
(a) 0.1 ? A
(b) l .0 ? A
(c) 10.0 ? A
(d) 100.0 ? A

Ans:-D

3. A D/A converter has 5 V full-scale output voltage and an accuracy of ±0.2 %. The maximum error for any output voltage
(a) Will be 5 mV
(b) Will be 10 mV
(c) Will be 20 mV
(d) Can be of any value depending on input

Ans:-B

4. An 8-input multiplexer is to be built with a tree - network of 2-input multiplexers. The number of 2-input multiplexers required is
(a) 4
(b) 8
(c) 6
(d) 7

Ans:-A

5. The contents of the control world register of INTEL 8253 (Programmable Interval Timer) is given below:
D7 D6 D5 D4 D3 D2 Dl D0
0 1 1 1 0 0 0 0
This control word sets
(a) Counter 0 to Mode 0
(b) Counter 1 to Mode 0
(c) Counter 2 to Mode 0
(d) Counter 0 to Mode 1

Ans:-B

6. RMS noise voltage at the input of a TV RF amplifier at the ambient temperature of 27° C is 30? V. The noise voltage at 90°C will be
(a) Zero
(b) 30 ? V
(c) 33 ? V
(d) 36.3 ? V

Ans:-C

7. A transmission line is distortion less f
(a) LC = RG
(b) LR = CG
(c) L = GCR
(d) LG = CR

Ans:-D

8. Consider the following statements regarding transmission lines transmitting high frequency (HF) signals:
HF transmission lines
1. Have appreciable ohmic and dielectric losses.
2. Have small physical length.
3. Are loss-free line
Of these statements:
(a) 1 and 2 are correct
(b) 2 and 3 are correct
(c) 3 alone is correct
(d) 1, 2 and 3 are correct

Ans:-A

9. Consider the following statements about SSB (Single Side Band) transmission:
1. It requires less power.
2. Transmitter and receiver needed are simple.
3. There is no interference.
4. Bandwidth required is less.
Of these statements
(a) 1, 2 and 3 are correct
(b) 1,2and4arecorrect
(c) 1 and 4 are correct
(a) 3 and 4 are correct

Ans:-C

10. In the narrow band FM system, the bandwidth is (fm is the modulating frequency)
(a) fm
(b) 2fm
(c) 3fm
(d) Of the same value as that for the wide band FM system

Ans:-B

11. In a double conversion AM receiver, the adjacent channel selectivity is determined mainly by
(a) The preselector and he RF stages
(b) The higher frequency IF stages
(c) The lower frequency IF stages
(d) Both the higher and lower frequency IF stages

Ans:-A

12. Consider the following statements regarding digital communication systems:
1. Pulse code modulation (PCM) is used
2. Quantisation noise occurs in PCM
3. In PCM, companding is used to protect small signals from quantisation distortion.
4. The Shannon-Hartley law describes signaling rates.
Of these statements:
(a) 2, 3 and 4 are correct
(b) 1, 3 and 4 are correct
(c) 1,2and4arecorrect.
(d) 1, 2 and 3 are correct

Ans:-D

13. With three geostationary satellites placed at the vertices of an equilateral triangle, what will the minimum lime that elapses (approximately), between the lime one earth station sends a message to another earth station located on the opposites side of the globe and the moment it receives a return response?
(a) 2 seconds
(b) 1.5 seconds
(c) 1 second
(d) 0.5 second

Ans:-D

14. Doppler effect is used in
(a) Pulsed radar
(b) CW radar
(c) MTI (moving target indicator)
(d) Both CW radar and MTI

Ans:-D

15. In a Wheatstone bridge, the known resistances are correct to within ±0.1%. The accuracy to which an unknown resistance can be measured is
(a) 0.4%
(b) 0.3%
(c) 0.2%
(d) 0.1%

Ans:-B

16. Match List (Unit) with List-II (Equivalent un it) and select the correct answer using the codes given below the lists:
List-I
A. Weber
B. Coulomb
C. Farad
List-II
1. Ampere-second per volt
2. Volt-second
3. Ampere-second
4. Volt per second
Codes:
A B C
(a) 1 2 3
(b) 2 3 1
(c) 2 3 4
(d) 3 1 4

Ans:-B

17. A special purpose diode which uses metals like gold, silver or platinum on one side of the Junction, n-type doped silicon on another side and has almost no charge storage in the junction, is a
(a) Schottky diode
(b) Tunnel diode
(c) Varactor diode
(d) zener diode

Ans:-A

18. Consider the following statements:
1. BJT needs bias stabilization because its I co increases with increase in VBE and temperature.
2. Thermal runaway may be avoided by choosing VCE < 1/2V CC
3. FET and BJT both need bias stabilization because both are semiconductor devices.
4. By increasing RE, bias stabilization improves.
Of these statements:
(a) 1 and 2 are correct
(b) 3 and 4 are correct
(c) 2 and 3 are correct
(d) 2 and 4 are correct

Ans:-A

19. Consider the following statements about Loran.
1. it is also known as hyperbolic system of navigation.
2. Standard Loran operates in the frequency range of 1.8 to 2.0 MHz.
3. In Loran, the synchronism between the master and the slave stations is achieved with the help of coaxial links.
4. The range of Loran can be enhanced to about 3500 km over the sea by using a frequency range of 90to 110 kHz
Of these statements:
(a) 1, 2 and 3 are correct
(b) 1, 3 and 4 are correct
(c) 1, 2 and 4 are correct
(d) 2, 3 and 4 are correct

Ans:-D

20. Match List I with List II and select the correct answer using the codes given below the lists:
List I
A. AM radio broadcast
B. FM radio broadcast
C. Microwave radio
D. Short wave radio and ratio telephony
List II
1. 2000 to 12000 MHz
2. 80 to l50 MHz
3. 300 Hz to 4 kHz
4. 500kHz to 3 MHz
5. 3 to 30 MHz
Codes:
A B C D
(a) 3 4 1 5
(b) 4 2 1 5
(c) 2 4 5 3
(d) 4 2 5 3

Ans:-D