Company: Hindustan Aeronautics Limited

HAL electronics and electrical free solved sample placement papers.

1 When a large number of analog signals is to be converted to digital form, an analog multiplex or is used. The A to D converter suitable in this case will be ..“
a.dual slope type
b.up down counter type
c.Successive approximation type-answer
d.forward counter type

2 In the formation of Routh’s array the situation of a row of zeros indicates that the system-
a.has symmetrically located roots.Answer not sensitive to variations in gain stable

3 Mark out wrong statement. Modulation is used to-
a.Reduce the bandwidth used-answer
b,Separate differing transmissions
c.Ensure that intelligence may be transmitted over long distances
d.Allow the use of practicable antennas

4 Mark out a wrong statement for two phase servo motor-
a.The rotor diameter is small
b.The rotor resistance is low-answer
c.The applied voltages are seldom balanced
d.The torque speed characteristic is linear.

5 The frequency deviation in phase modulation is-
a. independent of the modulating signal frequency-answer
b.inversely proportional to the modulating signal frequency
c.directly proportional to the modulating signal frequency.
d.inversely proportional to the square root of the modulating frequency.

6 Which power amplifiers has maximum efficiency?
a.Class A
b.Class AB
c.Class B-answer
d.Class C

8 Negative resistance characteristics for its operation is used by …..

9 The binary equivalent of 9.37510 is ……
a.1001.011 2-answer
b.1101.101 2
c.100.011 2
d.1111.001 2

10 The output signal amplitudes for1’s and 0’s in an ADM transmission system ….
a.Fixed and the repetition rate is also fixed
b.Fixed but the repetition rate is variable
c.Variable and the repetition rate is also variable
d.variable but the repetition rate is fixed-answer

11 For an RC driving point impedance function, the poles and zeros-
a.should alternate on real axis
b.should alternate only on the negative real axis-answer
c.should alternate on the imaginary axis
d.can lie anywhere on the left half place.

12 Mark out wrong statement regarding compandor-
It compresses the higher amplitude parts of a signal before modulation and expands them back to normal again after demodulation.
It gives preferential treatment to the weaker parts of the signal
For weaker signals, it gives a poor ratio of signal strength to quantizing error.-answer
Weaker signals, transverse more quantum steps than they would do otherwise and so quantizing error is reduced

13 Among other equipment a sub marine cable repeater contains …..

a.A dc power supply and regulator
b.Filters for the two directions of transmission-answer
c.Multiplexing and demultiplexing equipment
d.Pilot inject and pilot extract equipment

14 In a communication system noice is most likely to affect the signal-
a.At the transmitter
b.In the channel-answer
c.In the information source
d.At the destination

15 In gunn effect oscillator which mode having lowest operating frequency ….
b.Delayed domain mode
c.Quenched domain mode
d.LSA mode

16 In Reflex klystron maximum energy transferred to gap by electrons-
d.eR , ee, el-answer

17 The radio waves get absorbed by atmosphere depends –
a.Their distance from transmitter is long
b.Wave power is weak
c.Improper polarization of wave
dFrequency of waves-answer

18 8085 mP has no of sets of communication lines-

19 The diversity system in Troposcatter links is made use of to-
a.Increase the bandwidth
b.Prevent noise effects
c.Increase the directivity of the antenna.-answer
d.Detect signal in the presence of fading.

20 The plate efficiency of a class C amplifier is high because-
a.A resonant circuit is used as load
b.The plate current flows when the instantaneous plate voltage is low.
c. The plate current flows only when grid is driven positive-answer
d.None of the above

21 The Nyquist plot of G (jw), H (jw) for a closed-loop control system, passes through (-1,j0) point in the GH-plane. The gain margin o the system in dB is equal to

(a) infinite

(b) greater than zero

(c) less than zero

(d) zero (Ans)

Explanations : If the Nyquist plot of G (jw) H (jw) for closed-loop system passes through (-1 + j0) point, the gain margin is 1 and in dB

GM = -20 log 1 = 0

If the switch is opened, the total current supplied to the distribution system by the utility is

(a) 15.2 A

(b) 130.4 A

(c) 152 A (Ans)

(d) 13.04 A

Explanations : When the switch is opened, the power supplied to each load is

P1 = 3 V2f /Z cos q = 3 (480 V)2/10 Ω cos 300

= 59.86 kW

Q1 = 3 V2f /Z sin q = 3 (480 V)2/10 Ω sin 300

= 34.56 kW

P2 = 3 V2f /Z cos q = 3 (277 V)2/4 Ω cos 36.870

= 46.04 kW

Q2 = 3 V2f /Z sin q = 3 (277 V)2/4 Ω sin 36.870

= 34.53 kW

PTOT = P1 + P2 = 105.9 kW

QTOT = Q1 + Q2 = 69.09 kW

The apparent power supplied by the utility is

STOT = √P2TOT + Q2TOT = 126.4 kVA

The power factor supplied by the utility is

PF = cos tan-1 (QTOT /PTOT) = 0.838 lagging

The current supplied by the utility is

lL = PTOT/√3 VT PF = 105.9 kW/√3 (480 V) (0.838) = 152 A

22. Where is the hole concentration is greatest?

(a) x = 0

(b) x = L/2

(c) x = L (Ans)

(d) Uniform

Explanations : The hole concentration is greatest where Na is greatest, i.e., x = L.

23. Where is the electron concentration is greatest?

(a) x = 0 (Ans)

(b) x = L/2

(c) x = L

(d) Uniform

Explanations : The electron concentration is greatest where hole concentration is lowest, which is where Na is lowest.

Choose the most appropriate word from the options given below to complete the following sentence. Comparatively few rock musicians are willing to laugh at themselves, although a hint of ………. can boost sales of video clips very nicely.

(a) self-deprecation (Ans)

(b) congeniality

(c) cynicism

(d) embarrassment

Explanations : According to the sentence, very few musicians want to laugh at themselves, but this can boost the sale of video clips. So, option (a) is the best to complete this sentence.

24. In a direct election between two contestants, 4% of the votes cost are declared to be illegal. One contestant secures 55% of the valid votes and wins with a majority of 240 votes. What is the total number of votes cost ?

(a) 2455

(b) 2400

(c) 2500 (Ans)

(d) None of these

Explanations : Let total number of votes cost be x.

∴Total number of valid votes = 0.96 x

Winner contestant secures 55% of valid votes.

So, loser contestant secures 45% of valid votes.

∴ Majority = (55 – 45)% of valid votes

⇒ 240 = 10% of 0.96 x

⇒ x = 240/0.96 x 100/10 = 2500

25 There are two groups A and B consisting of 30 and 70 students respectively. If the average weight of group A is 30 kg and that of group B is 70 kg. Find the average weight of all the students of group A and group B.

(a) 58 kg (Ans)

(b) 50 kg

(c) 40 kg

(d) 12 kg

Explanations : Average weight of group A = 30 kg

Total weight of group A = 30 x 30 = 900 kg

Average weight of group B = 70 kg

Total weight of group B = 70 x 70 = 4900 kg

Average weight of group A and B = 900 + 4900
30 + 70

= 5000 = 58 kg