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Rites electronics and electrical questions

Rites ltd electronics questions with answers for practice

Rites Ltd electronics

Q.1 The two windings of a transformer is
(A) conductively linked.
(B) inductively linked.
(C) not linked at all.
(D) electrically linked.
Ans : B

Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will
(A) come to stop.
(B) continue to run at synchronous speed.
(C) continue to run at a speed slightly more than the synchronous speed.
(D) continue to run at a speed slightly less than the synchronous speed.
Ans: B

Q.3 The d.c. series motor should always be started with load because
(A) at no load, it will rotate at dangerously high speed.
(B) it will fail to start.
(C) it will not develop high starting torque.
(D) all are true.
Ans: A

Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about
(A) 50 Hz.
(B) 20 Hz.
(C) 2 Hz.
(D) Zero.
Ans: C

Q.5 In a stepper motor the angular displacement
(A) can be precisely controlled.
(B) it cannot be readily interfaced with micro computer based controller.
(C) the angular displacement cannot be precisely controlled.
(D) it cannot be used for positioning of work tables and tools in NC machines.
Ans: A

Q.6 The power factor of a squirrel cage induction motor is
(A) low at light load only.
(B) low at heavy load only.
(C) low at light and heavy load both.
(D) low at rated load only.
Ans: A

Q.7 The generation voltage is usually
(A) between 11 KV and 33 KV.
(B) between 132 KV and 400 KV.
(C) between 400 KV and 700 KV.
(D) None of the above.
Ans: A

Q.8 When a synchronous motor is running at synchronous speed, the damper winding produces
(A) damping torque.
(B) eddy current torque.
(C) torque aiding the developed torque.
(D) no torque.
Ans: D

Q.9 If a transformer primary is energised from a square wave voltage source, its output voltage will be
(A) A square wave.
(B) A sine wave.
(C) A triangular wave.
(D) A pulse wave.
Ans: A

Q.10 In a d.c. series motor the electromagnetic torque developed is proportional to
Option figure
Ans: B
Q.11 In a 3 – phase induction motor running at slip ‘s’ the mechanical power developed in terms of air gap power
11 and 12 figure
In a 3 – phase induction motor the maximum torque
(A) is proportional to rotor resistance
(B) does not depend on
(C) is proportional to
(D) is proportional to

Q.13In a d.c. machine, the armature mmf is
(A) stationary w.r.t. armature.
(B) rotating w.r.t. field.
(C) stationary w.r.t. field.
(D) rotating w.r.t. brushes.
Ans: C

Q.14In a transformer the voltage regulation will be zero when it operates at
(A) unity p.f.
(B) leading p.f.
(C) lagging p.f.
(D) zero p.f. leading.
Ans: B

Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of

Q.16 The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be
(A) 3.6 V.
(B) 2.5 V.
(C) 3.0 V.
(D) 6.0 V.
Ans: C

Q.17 The emf induced in the primary of a transformer
(A) is in phase with the flux.
(B) lags behind the flux by 90 degree.
(C) leads the flux by 90 degree.
(D) is in phase opposition to that of flux.
Ans: C

Q.18 The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a
(A) dc machine.
(B) 3 phase induction machine.
(C) synchronous machine.
(D) single phase induction machine.
Ans: all options are correct

Q.19 The current from the stator of an alternator is taken out to the external load circuit through
(A) slip rings.
(B) commutator segments.
(C) solid connections.
(D) carbon brushes.
Ans: C

Q.20 A motor which can conveniently be operated at lagging as well as leading power factors is the
(A) squirrel cage induction motor.
(B) wound rotor induction motor.
(C) synchronous motor.
(D) DC shunt motor.
Ans: C
Q.21 A hysteresis motor
(A) is not a self-starting motor.
(B) is a constant speed motor.
(C) needs dc excitation.
(D) can not be run in reverse speed.
Ans: B

Q.22
The most suitable servomotor for low power applications is
(A) a dc series motor.
(B) a dc shunt motor.
(C) an ac two-phase induction motor.
(D) an ac series motor.
Ans: B

Q.23 The size of a conductor used in power cables depends on the
(A) operating voltage.
(B) power factor.
(C) current to be carried.
(D) type of insulation used.
Ans: C

Q.24 Out of the following methods of heating the one which is independent of supply frequency is
(A) electric arc heating
(B) induction heating
(C) electric resistance heating
(D) dielectric heating
Ans: C
Q.25

A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be
(A) 4.5%.
(B) less than 4.5%.
(C) more than 4.5%.
(D) 4.5% or more than 4.5%.
Ans: C

Electronics Quiz

1. In a mercury arc rectifier

Ion stream moves from cathode to anode

Current flows from cathode to anode

Electron stream moves form anode to cathode

Ion stream moves from anode to cathode

.The answer is Ion stream moves from anode to cathode

2. For producing cathode spot in a mercury arc rectifier

An auxiliary electrode is used

Tube is evacuated

Low mercury vapour pressures are used

Anode is heated-Answer

.
3. If the voltage of anode B is raised to 510 V

Anode B will conduct but anode A will also continue to conduct

Anode B will not conduct but anode A will continue to conduct-Answer

Both anodes will not conduct

None of these

.
4. Ripple frequency of full wave rectifier working on 50 Hz supply will be

25 Hz-Answer

150 Hz

6 anode rectifier with inter phase transformer

All will have identical power factor

.
5. The form factor for half-wave rectifier sine wave is

1.05

1.15

1.45

1.57-Answer
6. A silicon controlled rectifier is a

Unijuction device

Device with three junctions-Answer

Device with four junctions

None of the above

.
7. For full-wave rectifier sine wave, form factor is

1.55

1.44

1.22

1.11-Answer

.
8. At absolute zero temperature a semi-conductor behaves as

An Insulator-Answer

A Super-Conductor

A Good Conductor

A Variable Resistor

.
9. An electron in the conduction band

Has higher energy than the electron in the valence band-Answer

Has lower energy than the electron in the valence band

Loses its charge easily

Jumps to the top of the crystal

.
10. EG for silicon is 1.12 eV and for germanium is 0.72 eV thus it can be conducted that

More number of electron-hole pairs will be generated in silicon than in germanium at room temperature

Less number of electron hole pairs will be generated in silicon than in germanium at room temperature-Answer

Equal number of electron hole pairs will be generated in both at lower temperatures

Equal number of electron hole pairs will be generated in both at higher temperatures

.
11. Before doping semiconductor material is generally

Dehydrated

Heated

Hardened

Purified-Answer

.
12. Select the one that is a acceptor impurity element

Antimony

Gallium-Answer

Arsenic

Phosphorous

.
13. At room temperature when a voltage is applied to an intrinsic semiconductor

Most of the electrons and holes move towards negative terminal

Most of the electrons and holes move towards positive terminal

Electrons move towards positive terminal and holes towards negative terminal-Answer

Electrons move towards negative terminal and holes towards positive terminal

.
14. Under which of the following conditions avalanche breakdown in a semiconductor diode takes place ?

When potential barrier is reduced to zero

When reverse bias exceeds a certain value-Answer

When forward bias exceeds a certain value

When forward current exceeds a certain value

.
15. Select the rectifier that needs four diodes

Half wave rectifier

Center-tap full wave rectifier

Bridge rectifier-Answer

None of the above

.
16. Maximum forward current in case of signal diode is in the range of

1A to 10A

0.1A to 1A

Few milli amperes-Answer

Few nano amperes

.
17. In a semiconductor avalanche breakdown takes place when

Reverse bias exceeds the limiting value-Answer

Forward bias exceeds the limiting value

Forward current exceeds the limiting value

Potential barrier is reduced to zero

.
18. The D.C output voltage from a power supply

Increases with higher values of filter capacitance and decreases with more load current-Answer

Decreases with higher values of filter capacitance and increases with more load current

Decreases with higher values of filter capacitance as well as with more load current

Increases with higher values of filter capacitance as well as with more load current

.
19. A solar cell provides a example of

Photo Voltaic Cell-Answer

Photo Conductive Cell

Photo Emissive Cell

Photo Radiation Cell

.
20. When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface, then it is expected that

No electrons are emitted-Answer

Hotons are emitted

Electrons of higher energy are emitted

Electrons of lower energy are emitted

.
21. An ideal diode should have

Zero resistance in the forward bias as well as reverse bias

Zero resistance in the forward bias and an infinitely large resistance in reverse bais-Answer

Infinitely large resistance in reverse bias

Infinitely large resistance in forward as well as reverse bais

.
22. The reverse resistance of a PN juction diode

Is always low

Is always high

Is given by breakdown voltage / reverse leakage current-Answer

Is given by forward voltage / reverse leakage current

.
23. In which case the temperature coefficient is positive

Intrinsic Semi-Conductor

Extrinsic Semi-Conductor-Answer

Both intrinsic as well as extrinsic semi-conductor

Neither intrinsic nor extrinsic semi-conductor

.
24. A PNP transistor is generally made of

Silicon

Germanium

Either silicon or germanium-Answer

None of the above

.
25. In a transistor the region that is very lightly doped and is very thin is

Emitter

Base-Answer

Collector

None of these

.
26. In a NPN transitor, when emitter junction is forward biased and collector junction is reverse biased, the transistor will operate in

Active Region-Answer

Saturated Region

Cut of Region

Inverted Region

.
27. A transistor will operate in inverted region if

Emitter junction is forward biased and collector junction is reverse biased

Emitter junction is reverse biased and collector junction is forward biased-Answer

Emitter junction as well as collector junction are forward biased

Emitter junction as well as collector junction are reverse biased

.
28. Which of the following is essential for transistor action ?

The base region must be very wide

The base region must be very narrow-Answer

The base region must be made of some insulating material

The collector region must be heavily doped

.
29. In a transistor, current ICBO flows when

Some D.C voltage is applied in the reverse direction to the emitter junction with the collector open circuited

Some D.C voltage is applied in the forward direction to the collector junction with the emitter open circuited

Some D.C voltage is applied in the reverse direction to the collector junction with the emitter open circuited-Answer

Some D.C voltage is applied in the forward direction to the emitter junction with the collector open circuited

.
30. The current Icbo

Increases with increase in temperature-Answer

Is normally greater for silicon transistors than germanium transistors

Mainly depends on the emitter base junction

Depends largely on the emitter doping

.
31. Thermal runway of a transitor occurs when

Heat dissipation from transistor is excessive

Transistor joints melt due to high temperature

There is excessive leakage current due to temperature rise-Answer

None of above
Rites Ltd electronics and electrical
Rites Limited electrical and electronics communication engg questions with answers,

1 The drain of an n-channel MOSFET is shorted to the gate so that VGS = VDS. The threshold voltage (VT) of MOSFET is 1 V. If the drain current (ID) is 1 mA for VGS = 2V, then for VGS = 3V, ID is

A) 2 mA
B) 3 mA
C) 9 mA
D) 4 mA

Answer : (D)

2 The first and the last critical frequency of an RC-driving point impedance function must respectively be

A) a zero and a pole
B) a zero and a zero
C) a pole and a pole
D) a pole and a zero

Answer : (D)

3 In what range should Re(s) remain so that the Laplace transform of the function e(a+2)t+5 exits?

A) Re (s) > a + 2
B) Re (s) > a + 7
C) Re (s) < 2
D) Re (s) > a + 5

Answer : (A)

4 A parallel plate air-filled capacitor has plate area of l0-4 m2 and plate separation of 10-3 m. It is connected to a 0.5 V, 3.6 GHz source. The magnitude of the displacement current is (e0 = 1/36p x 10-9 F/m)

A) 10 mA
B) 100 mA
C) 10 A
D) 1.59 mA

Answer : (A)

5 For the polynomial P(s) = s5 + s4 + 2s3 + 2s2 + 3s + 15, the number of roots which lie in the right half of the s-plane is

A) 4
B) 2
C) 3
D) 1

Answer : (B)

6 The phase velocity of an electromagnetic wave propagating in a hollow metallic rectangular waveguide in the TE10 mode is

A) equal to its group velocity
B) less than the velocity of light in free space
C) equal to the velocity of light in free space
D) greater than the velocity of light in free space

Answer : (D)

7 A device with input x(t) and output y(t) is characterized by: y(t) = x2(t). An FM signal with frequency deviation of 90 kHz and modulating signal bandwidth of 5 kHz is applied to this device. The bandwidth of the output signal is

A) 370 kHz
B) 190 kHz
C) 380kHz
D) 95kHz

Answer : (C)

8 The Q – meter works on the principle of

A) mutual inductance
B) self inductance
C) series resonance
D) parallel resonance

Answer : (C)

9 The Fourier transform of a conjugate symmetric function is always

A) imaginary
B) conjugate anti-symmetric
C) real
D) conjugate symmetric

Answer : (C)

10 An ideal op-amp is an ideal

A) voltage controlled current source
B) voltage controlled voltage source
C) current controlled current source
D) current controlled voltage source

Answer : (B)
11 A system has poles at 0.01 Hz, 1 Hz and 80 Hz; zeros at 5 Hz, 100 Hz and 200 Hz. The approximate phase of the system-response at 20 Hz is

A) – 90°
B) 0°
C) 90°
D) – 180°

Answer : (A)

12 In an abrupt p-n junction, the doping concentrations on the p-side and n-side are NA = 9x 1016/cm3 and ND = 1 x 1016/cm3 respectively. The p-n junction is reverse biased and the total depletion width is 3 m m. The depletion width on the p-side is

A) 2.7 mm
B) 0.3 mm.
C) 2.25 mm
D) 0.75 mm

Answer : (B)

13 A master-slave flip-flop has the characteristic that

A) change in the input immediately reflected in the output
B) change in the output occurs when the state of the master is affected
C) change in the output occurs when the state of the slave is affected
D) both the master and the slave states are affected at the same time

Answer : (C)

14 A parallel plate air-filled capacitor has plate area of l0-4 m2 and plate separation of 10-3 m. It is connected to a 0.5 V, 3.6 GHz source. The magnitude of the displacement current is (e0 = 1/36p x 10-9 F/m)

A) 10 mA
B) 100 mA
C) 10 A
D) 1.59 mA

Answer : (A)

15 The phase velocity of an electromagnetic wave propagating in a hollow metallic rectangular waveguide in the TE10 mode is

A)equal to its group velocity
B) less than the velocity of light in free space
C) equal to the velocity of light in free space
D) greater than the velocity of light in free space

Answer : (D)

16 Noise with uniform power spectral density of N0W/Hz is passed through a filter H (w) = 2 exp(-jwtd) followed by an ideal low pass filter of bandwidth BHz. The output noise power in Watts is

A) 2N0B
B) 4N0B
C) eN0B
D) 16 N0B

Answer : (B)

17 The cascade amplifier is a multistage configuration of

A) CC-CB
B) CE-CB
C) CB-CC
D) CE-CC

Answer : (B)

18 Consider a lossless antenna with a directive gain of +6dB. If 1 mW of power is fed to it the total power radiated by the antenna will be

A) 4 mW
B) 1 mW
C) 7 mW
D) 1/4 mW

Answer : (A)

19 The bandgap of Silicon at room temperature is

A) 1.3 eV
B) 0.7 eV
C) 1.1 eV
D) 1.4 eV

Answer : (C)

20 In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor

A) 8/6
B) 12
C) 16
D) 8

Answer : (C)

21 A device with input x(t) and output y(t) is characterized by: y(t) = x2(t). An FM signal with frequency deviation of 90 kHz and modulating signal bandwidth of 5 kHz is applied to this device. The bandwidth of the output signal is

A) 370 kHz
B) 190 kHz
C) 380kHz
D) 95kHz

Answer : (C)

22 For the polynomial P(s) = s5 + s4 + 2s3 + 2s2 + 3s + 15, the number of roots which lie in the right half of the s-plane is

A) 4
B) 2
C) 3
D) 1

Answer : (B)

23 An AM signal is detected using an envelope detector The carrier frequency and modulating signal frequency are 1 MHz and 2 kHz respectively. An appropriate value for the time constant of the envelope detector is

A) 500 msec
B) 20 msec
C) 0.2 msec
D) 1 msec

Answer : (B)

24 In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor

A) 8/6
B) 12
C) 16
D) 8

Answer : (C)

25 Consider the following statements S1 and S2.
S1: The b of a bipolar transistor reduces if the base width is increased.
S2: The b of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct?

A) S1 is FALSE and S2 is TRUE
B) Both S1 and S2 are TRUE
C) Both S1 and S2 are FALSE
D) S1 is TRUE and S2 is FALSE

Answer : (D)
26 A digital-to-analog converter with a full-scale output voltage of 3.5 V has a resolution close to 14m V. Its bit size is

A) 4
B) 8
C) 16
D) 32

Answer : (B)

27 A single-phase half-controlled rectifier is driving a separately excited dc motor. The dc motor has a back emf constant of 0.5 V/rpm. The armature current is 5 A without any ripple. The armature resistance is 2W. The converter is working from a 280 V, single phase ac source with a firing angle of 80°. Under this operating condition, the speed of the motor will be

A) 339 rpm
B) 359 rpm
C) 366 rpm
D) 386 rpm

Answer : (C)

28 In relation to the synchronous machines, which one of the following statements is false?

A) In salient pole machines, the direct-axis synchronous reactance is greater than the quadrature-axis synchronous reactance
B) The damper bars help the synchronous motor self start
C) Short circuit ratio is the ratio of the field current required to produce the rated voltage on open circuit to the rated armature current
D) The V-curve of a synchronous motor represents the variation in the armature current with field excitation, at a given output power

Answer : (C)

29A parallel plate air-filled capacitor has plate area of l0-4 m2 and plate separation of 10-3 m. It is connected to a 0.5 V, 3.6 GHz source. The magnitude of the displacement current is (e0 = 1/36p x 10-9 F/m)

A) 10 mA
B) 100 mA
C) 10 A
D) 1.59 mA

Answer : (A)

30 The 8085 assembly language instruction that stores the content of H and L registers into the memory locations 2050H and 2051H, respectively, is

A) SPHL 2050H
B) SPHL2051H
C) SHLD 2050H
D) STAX 2050H

Answer : (C)

31 If E is the electric field intensity, Ñ(Ñ x E ) is equal to

A) E
B) | E |
C) null vector
D) zero

Answer : (D)

32 The insulation strength of an EHV transmission line is mainly governed by

A) load power factor
B) switching over-voltages
C) harmonics
D) corona

Answer : (B)

33 The Q – meter works on the principle of

A) mutual inductance
B) self inductance
C) series resonance
D) parallel resonance

Answer : (C)

34 A 800 kV transmission line is having per phase line inductance of 1.1 mH/km and per phase line capacitance of 11.68 nF/km. Ignoring the length of the line, its ideal power transfer capability in MW is

A) 1204 MW
B) 1504 MW
C) 2085 MW
D) 2606 MW

Answer : (C)

35 In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor

A) 8/6
B) 12
C) 16
D) 8

Answer : (C)

36 At an industrial sub-station with a 4 MW load, a capacitor of 2 MVAR is installed to maintain the load power factor at 0.97 lagging. If the capacitor goes out of serivce, the load power factor becomes

A) 0.85
B) 1.00
C) 0.80 lag
D) 0.90 lag

Answer : (C)

37The conduction loss versus device current characteristic of a power MOSFET is best approximated by

A) a parabola
B) a straight line
C) a rectangular hyperbola
D) an exponentially decaying function

Answer : (A)

38 High Voltage DC (HVDC) transmission is mainly used for

A) bulk power transmission over very long distances
B) inter-connecting two systems with the same nominal frequency
C) eliminating reactive power requirement in the operation
D) minimizing harmonics at the converter stations
Answer : (A)

39 For the equation,

s3 – 4s2+ s + 6 = 0
the number of roots in the left half of s-plane will be

A) 0
B) 1
C) 2
D) 3

Answer : (C)

40 For the function f(x) = x2 e-x, the maximum occurs when x is equal to

A) 2
B) 1
C) 0
D) -1

Answer : (B)
Rites computer and electronics engg questions

Rites ltd computer engg questions and answers for practice

1 The problems 3-SAT and 2-SAT are
A) both in P
B) both NP-complete
C) NP-complete and in P respectively
D) undecidable and NP-complete respectively
Answer : (C)

2 Consider the following relation schema pertaining to a students database: Student (rollno, name, address) Enroll (rollno, courseno, coursename)
where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where ‘*’denotes natural join?
A) 8, 8
B) 120, 8
C) 960, 8
D) 960, 120
Answer : (C)

3 Consider a relation scheme R = (A, B, C, D, E, H) on which the following functional dependencies hold : (A -> B, BC -> D, E -> C, D -> A). What are the candidate keys of R?
A) AE, BE
B) AE, BE, DE
C) AEH, BEH, BCH
D) AEH, BEH, DEH
Answer : (D)

4 The goal of structured programming is to
A) have well indented programs
B) be able to infer the flow of control from the compiled code
C) be able to infer the flow of control from the program text
D) avoid the use of GOTO statements
Answer : (C)

5 The tightest lower bound on the number of comparisons, in the worst ease, for comparison-based sorting is of the order of
A) n
B) n 2
C) n log n
D) n log2 n
Answer : (B)

6 A circuit outputs a digit in the form of 4 bits. 0 is represented by 0000,1 by 0001,…, 9 by 1001. A combinational circuit is to be designed which takes these 4 bits as input and outputs 1 if the digit ³ 5, and 0 otherwise. If only AND, OR and NOT gates may be used, what is the minimum number of gates required
A) 2
B) 3
C) 4
D) 5
Answer : (C)

7 WA and B are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both A and B attempt to transmit a frame, collide, and A wins the first backoff race. At the end of this successful transmission by A, both A and B attempt to transmit and collide. The probability that A wins the second backoff race is
A) 0.5
B) 0.625
C) 0.75
D) 1.0
Answer : (A)

8 If 73x (in base-x number system) is equal to 54y (in base-y number system), the possible values of x and y are
A) 8, 16
B) 10, 12
C) 9, 13
D) 8, 11
Answer : (D)

9 In a packet switching network, packets are routed from source to destination along a single path having two intermediate nodes. If the message size is 24 bytes and each packet contains a header of 3 bytes, then the optimum packet size is
A) 4
B) 6
C) 7
D) 9
Answer : (D)

10 A Priority-Queue is implemented as a Max-Heap. Initially, it has 5 elements. The level-order traversal of the heap is given below: 10, 8,5,3,2 Two new elements 1 and 7 are inserted in the heap in that order. The level-order traversal of the heap after the insertion of the elements is
A) 10,8,7,5,3,2,1
B) 10,8,7,2,3,1,5
C) 10,8,7,1,2,3,5
D) 10,8,7,3,2,1,5
Answer : (D)

11 Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used is First Come First Served (FCFS). If FCFS is replaced by Shortest Seek Time First (SSTF), claimed by the vendor to give 50% better benchmark results, what is the expected improvement in the I/O performance of user programs ?
A) 50%
B) 40%
C) 25%br> D) 0%
Answer : (D)

12 How many distinct binary search trees can be created out of 4 distinct keys?
A) 5
B) 14
C) 24
D) 42
Answer : (B)
Q-13 Select the one true statement. A) Every binary tree is either complete or full.
B) Every complete binary tree is also a full binary tree.
C) Every full binary tree is also a complete binary tree
D) No binary tree is both complete and full.

Q-14 Which data structure has the fastest insertion procedure? A) Binary search tree
B) Ordered array
C) Heap
D) Unordered linked list
E) Ordered linked list

Q-15 What are the complexities of the insert, remove and search methods of a binary search tree in the worst case? A) insert is O(n), remove is O(n), search is O(n)
B) insert is O(log n), remove is O(log n), search is O(n)
C) insert is O(log n), remove is O(log n), search is O(log n)
D) insert is O(log n), remove is O(log n), search is O(1)
E) These methods can’t be defined on a binary search tree

Q-16 This Ethernet frame type is characterized by its use of the code AA in the SAP fields. A) Ethernet II
B) Ethernet RAW
C) Ethernet 802.2
D) Ethernet SNAP

Q-17 Which of the following are examples of routed protocols? (Choose all that apply) A) IP
B) IPX
C) RIP
D) OSPF
E) AppleTalk

Q-18 If switches are used to replace hubs on a network, which of the following statements is true? A) The number of broadcast domains will decrease
B) The number of collision domains will increase
C) The number of collision domains will decrease
D) The number of broadcast domains will be zero

Q-19 Full duplex Ethernet communication is only possible when:

A. Systems are connected to same LAN segments
B. Systems are connected to a bridged ports
C. Systems are connected to their own switch port
D. Systems are running over a fiber optic connection

Q-20 SQL is the combination of

A ) DDL and DQL
B ) DDL , DML and DQL
C ) DDL,DML,DQL and DCL
D ) None of these

Q-21 Which of the following applications may use a stack?

A) A parentheses balancing program.
B) Keeping track of local variables at run time.
C) Syntax analyzer for a compiler.
D) All of the above

Q -22 Consider the implementation of the Stack using a partially-filled array. What goes wrong if we try to store the top of the Stack at location [0] and the bottom of the Stack at the last used position of the array?

A) Both peek and pop would require linear time.
B) Both push and pop would require linear time.
C) The Stack could not be used to check balanced parentheses.
D) The Stack could not be used to evaluate postfix expressions.

Q-23 Select the one true statement.
A) Every binary tree is either complete or full.
B) Every complete binary tree is also a full binary tree.
C) Every full binary tree is also a complete binary tree
D) No binary tree is both complete and full.

Q-24 Which data structure has the fastest insertion procedure? A) Binary search tree
B) Ordered array
C) Heap
D) Unordered linked list
E) Ordered linked list

Q-25 What are the complexities of the insert, remove and search methods of a binary search tree in the worst case? A) insert is O(n), remove is O(n), search is O(n)
B) insert is O(log n), remove is O(log n), search is O(n)
C) insert is O(log n), remove is O(log n), search is O(log n)
D) insert is O(log n), remove is O(log n), search is O(1)
E) These methods can’t be defined on a binary search tree

Q-26 This Ethernet frame type is characterized by its use of the code AA in the SAP fields.
A) Ethernet II
B) Ethernet RAW
C) Ethernet 802.2
D) Ethernet SNAP

Q-27 Which of the following are examples of routed protocols? (Choose all that apply) A) IP
B) IPX
C) RIP
D) OSPF
E) AppleTalk

Q-28 If switches are used to replace hubs on a network, which of the following statements is true? A) The number of broadcast domains will decrease
B) The number of collision domains will increase
C) The number of collision domains will decrease
D) The number of broadcast domains will be zero

Q-29 Full duplex Ethernet communication is only possible when:

A. Systems are connected to same LAN segments
B. Systems are connected to a bridged ports
C. Systems are connected to their own switch port
D. Systems are running over a fiber optic connection

Q-30 SQL is the combination of

A ) DDL and DQL
B ) DDL , DML and DQL
C ) DDL,DML,DQL and DCL
D ) None of these

Q-31 Which of the following applications may use a stack?

A) A parentheses balancing program.
B) Keeping track of local variables at run time.
C) Syntax analyzer for a compiler.
D) All of the above

Q -32 Consider the implementation of the Stack using a partially-filled array. What goes wrong if we try to store the top of the Stack at location [0] and the bottom of the Stack at the last used position of the array?

A) Both peek and pop would require linear time.
B) Both push and pop would require linear time.
C) The Stack could not be used to check balanced parentheses.
D) The Stack could not be used to evaluate postfix expressions.

Section-2 electronics and electrical

1. The ability of a material to remain magnetized after removal of the magnetizing force is known as

Permeability
reluctance
hysteresis
retentivity
Ans:D

2. When a solenoid is activated, the force that moves the plunger is

an electromagnetic field
a permanent magnetic field
varying voltage
a steady current
Ans:A

3. Which of the following capacitors is polarized

mica
ceramic
plastic-film
electrolytic
Ans:D

4. In a series resonant band-pass filter, a lower value of Q results in

a higher resonant frequency
a smaller bandwidth
a higher impedance
a larger bandwidth
Ans:D

5. A steady-state condition is reached when

the output voltage reaches the average value of the input voltage
the output voltage reaches the input voltage
the output voltage reaches approximately 63% of the input voltage
the output voltage reaches the effective value of the input voltage
Ans:A

6. An RC differentiator acts as a

low-pass filter
high-pass filter
band-pass filter
band-stop filter
Ans:B

7. A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is

1500 r.p.m.
1425 r.p.m.
25 r.p.m.
75 r.p.m.
Ans:D

Explanation: NS = 120f /P = 120 x 50 /4 =1500rpm

N = NS ( 1-s) = 1500 (1-0.05) = 1425

\relative speed = 1500 – 1425 = 75 rpm

8. A ceiling fan uses

split-phase motor.
capacitor start and capacitor run motor
universal motor.
capacitor start motor.
Ans:D

9. The drive motor used in a mixer-grinder is a

dc motor.
induction motor.
synchronous motor.
universal motor.
Ans:D

10. A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals

0.2 Amp.
5 Amps
10 Amps.
20 Amps.
Ans:A
Explanation: I1= V1 /R1 = 120/600 = 0.2 (h = 100%, losses are zero \V1 = VR = I1R1)

11. A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of

poles of the motor are

4.
6.
12
8.
Ans:A

Explanation: N= Ns (1-S) = NS –NS x S

1440 = Ns (1-S)

Ns = 1440 / (1-S)

Ns = (120 f/ p) = 120 x 50/p = 6000 p

Ns will be closer to N i.e 1440

When P=2 ; Ns = 3000 rpm , not close to N

When P=4 ; Ns = 1500 rpm , it is closer to N

Therefore P =4 for N=1440

12. In a 3-phase synchronous motor

the speed of stator MMF is always more than that of rotor MMF.
the speed of stator MMF is always less than that of rotor MMF.
the speed of stator MMF is synchronous speed while that of rotor MMF is zero
rotor and stator MMF are stationary with respect to each other.
Ans:D

Explanation: Because, Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction Therefore,

rotor & stator mmf are stationary w.r.t each other.

13. In a three phase transformer, if the primary side is connected in star and secondary

side is connected in delta, what is the angle difference between phase voltage in the

two cases.

delta side lags by -30°.
star side lags by -30°.
delta side leads by 30°.
star side leads by -30°.
Ans:C

Explanation: This is vector group and has +30° displacement. Therefore, delta side leads by +30°.
14. Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz.

What will be the frequency of the rotor induced emf?
10 Hz.
50 Hz.
1 Hz.
2500 Hz.
Ans:C
Explanation: Given : s = 0.02 ; f = 50 Hz

Therefore, frequency of rotor induced emf = s f

= 0.02 x 50 = 1.0 Hz

15. A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf?

100 Volts.
0.1 Volts.
1 Volts.
10 Volts.
Ans:D

Explanation: Given N = 1500 rpm, F = 0.4 mWb, Z = 1000, P = 4, & A= 4

Therefore, Eb = NFPZ / 60 A

= 1500 x 0.4 x 4 x 1000 x 10-3 / 60 x 4

= 60/6 = 10 volts

Rites chemical engg questions
Rites Ltd chemical engg questions for practice ,Rites ltd practice questions, This is only for practice questions, Rites mechanical engg questions with answers, Rites previous years solved practice question papers, Rites free solved sample placement papers

Rites Ltd chemical engg questions

1 Why beating is required in the manufacture of pulp?
2 Mention the steps involved in the manufacture of sugar
3 What are the uses of bagasse?
4 What are the industrial applications of starch?
5 Name four industrial fermentation products
6 What is meant by hydrogenation in oil and fat industry?
7 What are soaps and detergents?
8 What are the uses of fatty acids?
9 What are the byproducts from natural gasoline?
10 What are heavy distillates?
11 What are the characteristics of petroleum refining?
12 What is meant by catalytic reforming?
13 How are plastics classified?
14 What are the ways in which polymerization takes place?
15 Name three synthetic fibers
16 Give one example of polyester
17 Name three synthetic rubbers
18 Name two tanning processes in leather industry
19 Vegetable tanning is used for what type of materials?
20 Classify the dyes
Part B (5 x 12 = 60 Marks)

(a) Describe the manufacture of sulphate pulp including black liquor recovery
Or

(b) Discuss the various gasification processes of coal with neat diagram

(a) Describe the manufacture of industrial alcohol from molasses with the help of a flow chart
Or

(b) What is soap? How is soap manufactured?

(a) Discuss the products obtained from the refining of petroleum and indicate their commercial uses
Or

(b) What is sweetening? List the different sweetening treatments used in petroleum processing. Discuss any one method in detail

(a) What are plastics? What are the basic differences between thermoplastic, thermosetting and elastomer resins. Give examples
Or

(b) (i) Discuss about different types of resins

(ii) Describe the manufacture of phenol-formaldehyde resin with a neat flow diagram (5 + 7)

(a) Describe the viscose process for the manufacture of Rayon fiber indicating in detail the steps involved
Or

(b) (i) Compare natural and synthetic rubbers

(ii) How is natural rubber prepared? What are its important properties (6 + 6)

Process Calculations – Problems

1 1000 litres of a mixture of H2, N2 and CO2 at 150oC was found to have the following ratio for the partial pressures of the gases: PH2 : PN2 : PCO2 is 1:4:3. If the total pressure is 2 atm absolute, calculate
a)Mole fraction of each of these gases.
b)Weight percent of each of these gases.
c)Average molecular weight and
d) Weight of CO2 in kg.

2 A dryer with a capacity of 800 kg/day operates on a material which is 90% H2O and 10% solid. The product which contains 20% H2O is dried in another dryer until the water content is 2%. Calculate the % of the original water which is removed in each dryer and the weight of product from each dryer.

3 In order to obtain barium in a form that may be put into solution, the natural barytes, containing only pure barium sulfate and infusible matter, is fused with an excess of pure, anhydrous soda ash. Upon analysis of the fusion mass it is found to contain 11.3% barium sulfate, 27.7% sodium sulfate and 20.35% sodium carbonate. iThe remainder is barium carbonate and infusible matter. Calculate
iiThe % conversion of barium sulfate to barium carbonate
iiiThe composition of original barytes and The % excess of sodium carbonate used above the theoretical amount required for reaction with all the barium sulfate.
4 Air at a temperature of 20oC and 750 mm Hg has a relative humidity of 80%. Calculate
i the molal humidity of the air
ii the molal humidity of this air if its temperature is reduced to 10oC and pressure increased to 2000 mm Hg condensing out some of the water, and
iii weight of water condensed from 1000 litres of the original wet air in cooling and compressing to the conditions of part (ii).
Vapor pressure of water at 20oC = 17.5 mm Hg
Vapor pressure of water at 10oC = 9.2 mm Hg.
5 A fuel oil containing 88.2% Carbon and 11.8% Hydrogen (by weight) is burnt with 20% excess air. 95% of the carbon is burnt to carbon dioxide and the rest to carbon monoxide. All the hydrogen is converted to water. Determine the Orsat analysis of the flue gas.
6 A furnace uses a natural gas which consists of entirely hydrocarbons. The flue gas analysis is CO2 : 9.5%, O2 : 1.4%, CO : 1.9% and the rest to N2. Calculate
i atomic ratio of hydrogen to carbon in the fuel
ii percentage excess air used
iii composition of the fuel gas in the form CxHy.
7 The gases from a sulfur have the following analysis: SO2 : 9.86%, O2 : 8.54%, N2 : 81.6%. After passage of the gases through a catalytic converter, the analysis (SO3 free basis) is SO2 : 0.6%, O2 : 4.5%, N2 : 94.9%. What % of the SO2 entering the converter has been oxidized to SO3?
8 The analysis of gas entering the converter in Contact H2SO4 plant is SO2 : 4%, O2 : 13% and N2 : 83% (on volume basis). The gas leaving the converter contains 0.45% SO2 on SO3 free basis (by volume). Calculate the % of SO2 entering the converter getting converted to SO3.
9 17.2 grams of N2O4 gas, when heated to 100oC at 720 mm Hg undergoes 90% dissociation according to the equation N2O4 à 2NO2. Calculate the volume occupied at 100oC and 720 mm Hg assuming ideal gas law.

10 A gaseous mixture contains 1 kg of helium, 5 kg of ammonia and 10 kg of nitrogen at 344.1 K and 2 atm absolute pressure. Calculate:
i the composition in mole percent
ii the partial pressure of each component
iiithe molal density of the mixture, and
iv the average molecular weight.
11 A solvent recovery system delivers gas saturated with benzene vapor which analyses on a benzene-free basis 15% CO2, 4% O2 and 81% N2. This gas is at 21.1oC and 750 mm Hg pressure. It is compressed to 5 atmosphere and cooled to the same temperature after compression. How many kg of benzene are condensed by this process per 1000 m3 of the original mixture if the vapor pressure of at 21.1oC is 75 mm Hg?
12 A distillation column separates an ethyl alcohol feed into high purity alcohol and waste water. The feed has a composition of 20 mole percent of ethyl alcohol. The distillate contains 85 mole percent ethyl alcohol and the bottoms have a 3 mole percent alcohol concentration. If the feed is charged to the column at the rate of 45 kmol/hr, calculate
i the quantity of distillate and bottoms
ii what percentage of alcohol in the feed is recovered in the distillate?
13 In a causticization process, NaOH is produced by adding a solution containing 10% by weight of sodium carbonate in the stoichiometric proportions to an inlet slurry containing 25% by weight of calcium hydroxide. If the inlet slurry is charged at the rate of 100 kg/hr, what would be the composition of the final slurry if the reaction goes to 99% completion? What is the amount of sodium hydroxide produced?
14 Formaldehyde is manufactured by the catalytic oxidation of methanol using an excess of air according to the reaction I. A secondary oxidation II also occurs if the conditions are not properly controlled.
CH3OH + 0.5O2 à HCHO + H2O — I

HCHO + 0.5O2 à HCOOH — II

In a test run the product gases have the following composition by volume: CH3OH = 8.6% ; HCHO = 3.1% ; HCOOH = 0.6% ; H2O = 3.7% ; O2 = 16.0% ; N2 = 68%. Calculate the following:
Percentage conversion of methanol to formaldehyde
Percentage of methanol lost due to reaction II.
Molar ratio of air to methanol used.
15 Natural gas containing CH4 = 83% and C2H6 = 17% was burnt with an excess of dry air. The Orsat analysis of the flue gas was CO2 = 6.76% ; CO = 2.77% ; O2 = 5.63% ; N2 = 84.84%. Calculate the following:
percentage excess air supplied
percentage completion of oxidation of carbon
amount of fuel gas produced per 100 m3 of fuel at 500oC and 1 atmosphere pressure.
16 Carbon dioxide is produced by recovering CO2 from flue gas. The flue gas is passed up through an absorber in contact with an aqueous solution of Na2CO3. The flue gas contains 20 percent (by volume) of CO2. The effluent gas from the absorber contains 9 percent CO2 (by volume). How many kg moles of flue gas are required to produce 1000 kg of CO2 if 90 percent of the CO2 absorbed is recovered as product?
17 8000 kg of an aqueous solution containing 25 percent (by weight) of anhydrous sodium sulfate are fed to a crystallizer. The solution is cooled and 15% of the initial water is lost by evaporation. Na2SO4.10H2O crystallizes out. If the mother liquor (solution after crystallization) contains 18.3% (by weight) of anhydrous Na2SO4, calculate the weight of mother liquor and crystals obtained.
18 Air at 1 atmosphere (absolute) and 40oC containing 0.053 kmol water/ kmol of dry air is to be conditioned to 30oC containing 0.018 kmol of water/ kmol of dry air by cooling part of the air to 25oC containing 0.012 kmol of water/ kmol of dry air and mixing it with the uncooled air. The resulting mixture is reheated to 30oC. For 1000 m3/min of wet air at 30oC and containing 0.018 kmol of water/ kmol of dry air, calculate:
volume of entering wet air, and
percentage of entering air which is bypassed.
19 In a process to manufacture HCl, common salt and sulfuric acid are heated together. The HCl gas produced is cooled and absorbed in water to produce 31.5% HCl (by weight). Some HCl is lost during absorption. To produce 1 ton of 31.5% HCl, 550 kg of common salt and 480 kg of 98% H2SO4 were taken. The reaction goes to completion. Calculate:
Which reactant is in excess?
What is the amount of HCl lost?
Calculate the composition and quantity of residue left behind when 50% of water is distilled off.
20 A liquid containing 47.5% acetic acid and 52.5% water is to be separated by solvent extraction using isopropanol. The solvent used is 1.3 kg per kg of feed. The final extract is found to contain 82% acid on solvent free basis. The residue has 14% acid on solvent free basis. Find the percentage extraction of acid from the feed.
21 When heated to 100oC and 720 mm Hg pressure, 17.2 gm of N2O4 gas occupy a volume of 11.45 litres. Assuming that ideal gas law applies calculate the % dissociation of N2O4 to NO2.
22 Paper is passing continuously through a tunnel drier. The entering paper contains 10 % water (dry basis i.e., 10 kg water/100 kg dry paper) and the leaving paper contains 2% water (dry basis). How many kg of water is evaporated per hour if 1000 kg/hr of paper enters the drier?
23 Chlorobenzene is nitrated using mixed acid. A charge consisted of 100 kg of chlorobenzene, 106.5 kg of 65.5% nitric acid, and 93.6% sulfuric acid. After 2 hours of operation it was found that 2% of the feed chlorobenzene remained unreacted and the product distribution was 66% p-nitrochlorobenzene and 34% o-nitrochlorobenzene.

Calculate the analysis of charge
percentage conversion of chlorobenzene
the composition of the products.
24 In a vessel at 200 kN/m2 and 310 K, % relative humidity of water vapor in air is 25. The partial pressure of water vapor when air is saturated with vapor at 310 K is 6.3 kN/m2. Calculate:
humidity of air Percentage humidity

.
25 Carbon tetra chloride is to be removed from a polymer solution by bubbling dry air through it at 297 K. The resulting mixture has % relative humidity of 70. It is required to remove 90% of carbon tetra chloride present by cooling to 283 K, and compressing to a suitable pressure. What this pressure should be?
Data: Vapor pressure of CCl4 at 297 K = 12.2 kN/m2 and at 283 K = 6 kN/m2

26 280 kg of nitrogen and 64.5 kg of hydrogen are brought together and allowed to react at 515oC and 300 atm pressure and from the experimental measurements it is found that there are 38 kmol of gases present at equilibrium.
How many kmol of N2 and H2 and ammonia are present at equilibrium?
Which is the limiting and which is the excess reactant?
How much excess hydrogen is there?
What is the amount of theoretically required hydrogen?
What is the percentage conversion of hydrogen to ammonia?
27 Methanol is produced by the reaction of carbon monoxide with hydrogen.
CO + 2H2 à CH3OH. — I

The side reaction is

CO + 3H2 à CH4 + H2O — II

At a pressure of 70.3 kgf/cm2 (absolute) and a temperature of 301.5oC, the conversion per pass is 12.5%, and of this amount 87.5% is assumed to react via equation I and 12.5% via equation II. The stream leaving the reactor passes through a condenser and a separator. Carbon monoxide and hydrogen, leaving this unit are recycled. The leaves as a gas and the liquid mixture of methanol and water passes to a distillation column for the concentration of methanol. Fresh feed gas contains 32 mole % CO and 68 mole % H2 at 65.5oC and 70.3 kgf/cm2 (absolute). Recycle stream is also at 70.3 kgf/cm2 (absolute) and 301.5oC. Calculate:

Analysis, mole % and weight % of hot gaseous stream leaving the reactor.
Methanol content, weight % of liquid (Methanol + water) stream, leaving the condenser and separator.
Recycle ratio expressed as kg of CO and H2 recycled per kg of fresh feed gas.
28 What will be the composition of the gases obtained by burning pure FeS2 with 60% excess air? Assume that the reaction proceeds in the following manner:
4FeS2 + 11O2 à 2Fe2O3 + 8SO2.

29 Calculate the total pressure and the composition of vapors in contact with a solution at 100oC containing 35% benzene, 40% toluene and 25% xylene by weight.
Data: Vapor pressures at 100oC Benzene: 1340 mm Hg
Toluene: 560 mm Hg
Xylene: 210 mm Hg
30 Two engineers are calculating the average molecular weight of a gaseous mixture containing oxygen and other gases. One of them using the correct molecular weight of 32 determines the average molecular weight correctly as 39.2. The other using an incorrect value of 16 determines the average molecular weight as 32.8. This is the only error in the calculations. What is the amount of oxygen in the mixture expressed in mole % and weight %?
31 Pure carbon dioxide may be prepared by treating limestone with dilute sulfuric acid. The limestone contains CaCO3 and MgCO3 with a small quantity of inert matter. The acid used is 12% H2SO4. During the process the mass was warmed and CO2 and water vapor were removed. The residue from the process has the following composition:
CaSO4 8.56%
MgSO4 5.23%
H2SO4 1.05%
Inerts 0.53%
CO2 0.12%
Water 84.51%
———–
Total 100.00%
———–
Calculate the following:

The analysis of limestone used; and
The percentage of excess acid used.
32 Antimony (Sb) is produced by heating powdered Sb2S3 and Fe and removing molten Sb from the reaction vessel. If 1.8 kg of Sb2S3 and 1.3 kg of Fe are heated to give 0.9 kg of Sb, calculate
Limiting and excess reactants
Percentage excess reactant
Degree of completion
Percentage conversion.
33 Natural gas containing 80% CH4, 15% C2H6 and 5% C3H8 is burnt with 50% excess air. Assuming that 90% of the hydrocarbons are converted to CO2 and the rest to CO, determine
Fuel gas analysis
Orsat analysis
34 The gaseous reaction A à 2B + C takes place isothermally in a constant pressure reactor. Starting with a mixture of 75% A and 25% inerts (by volume), in a specified time the volume doubles. Calculate the conversion achieved.
35 In the Deacon process for manufacturing chlorine, hydrochloric acid gas is oxidized with air. The reaction taking place is
4HCl + O2 à 2Cl2 + 2H2O

If the air is used in excess of 30% of that theoretically required, and if the oxidation is 80% complete, calculate the composition by volume of dry gases leaving the reaction chamber.

36 In a particular crystallization process, 2500 kg of Na2SO4.12H2O crystals are obtained. The mother liquor leaving the process contains 20% Na2SO4 anhydrous by weight. If the feed solution contains 35% Na2SO4 and 25% of the original H2O is lost by evaporation, determine:
weight of original solution and mother liquor
percentage recovery
37 Nitrogen from a cylinder is bubbled through acetone at 1.1 bar and 323 K at the rate of 2 x 10-4 m3/min. The nitrogen, saturated with acetone vapor leaves at 1.013 bar, 308 K at the rate of 3.83 x 10-4 m3/min. What is the vapor pressure of acetone at 308 K?
38 Limestone mixed with coke is being burnt in a kiln. An average analysis of the limestone is CaCO3 : 84.5%, MgCO3 : 11.5% and the rest inerts. The coke contains 76% carbon, 21% ash and 3% moisture. The calcination of CaCO3 is only 95% complete and that of MgCO3 is 90%. The carbon in the coke is completely burnt to CO2. The kiln is fed with 1 kg of coke per 5 kg of limestone. Calculate weight percent CaO in the product leaving the kiln.
39 Pure propane (C3H8) is burnt in an excess of air to give the following analysis of combustion products in volume percent:
CO2 = 5.0, CO = 3.5, H2O = 11.4, O2 = 7.0 and N2 = 73.1
Calculate the percentage of excess air used.

40 A mixture of NH3 and air at 720 mm Hg and 40o contains 6.3% NH3 by volume. The gas is passed at the rate of 100 m3/hr through an absorption tower in which only NH3 is removed. The gases leave the tower at 715 mm Hg and 30oC containing 0.09% NH3 by volume. Using ideal gas law, calculate
Rate of flow of gas leaving the absorber.
Weight of NH3 absorbed in kg/hr
41 The analysis of 15000 litre of gas mixture at standard conditios is as follows:
CO2 = 9.5% ; SO2 = 0.5% ; O2 = 12.0% ; N2 = 78.0%.
How much heat must be added to this gas to change its temperature from 25oC to 700oC?
Data: Specific heat values in kcal/(kmol.oK)
Gas CO2 SO2 O2 N2
Cp at 25oC 8.884 9.54 7.017 6.961
Cp at 700oC 11.303 11.66 7.706 7.298
42 10 kmol of zinc are to be heated from 0oC to 1000oC. It melts at 419oC and boils at 907oC. Determine the heat required for the process.
Data:
Cpm of solid Zn = 0.105 kcal/kg oC
Cpm of molten Zn = 0.109 kcal/kg oC
Cpm of vapor Zn = 4.97 kcal/kmol
l vap = 26900 kcal/kmol

Use Trouton’s rule to estimate the latent heat of melting.

43 An evaporator is fed with10000 kg/hr of a solution containing 1% solute by weight. It is to be concentrated to 1.5% solute by weight. The feed is at a temperature of 37oC. The water is evaporated by heating with steam available at a pressure of 1.34 atm absolute, corresponding to a temperature of 108.3oC. The operating pressure in the vapor space is 1 atm absolute. Boiling point elevation and other effects can be neglected. The condensate leaves at the condensing temperature. All the physical properties of the solution may be taken to be same as that of water. What is the quantity of steam required per hour? What is the quantity of steam required per hour?
Data:
Enthalpy of feed = 38.1 kcal/kg
Enthalpy of solution inside the evaporator (at 100oC) = 644 kcal/kg
Enthalpy of vapor at 100oC = 644 kcal/kg
Latent heat of vaporization of steam = 540 kcal/kg

44 Calculate the theoretical flame temperatre of a gaseous fuel containing 20% CO, and 80% N2 when burnt with 100% excess air, both air and gas initially being at 25oC. Heat of combustion of carbon monoxide = 67636 kcal/kmol.
Data: Specific heats of products of combustion in kcal/(kmol.oK)
Carbon dioxide: Cp = 6.339 + 10.14 x 10-3T
Oxygen: Cp = 6.117 + 3.167 x 10-3T
Nitrogen: Cp = 6.457 + 1.389 x 10-3T
where T = temperature in Kelvin

45 100 kg/hr of an organic ester of formula C19H36O2 is being hydrogenated to C19H38O2 by a continuous process. The company purchases its hydrogen in cylinders of 10 m3 capacity initially at 70 bar and 303 K. If the company buys 50 days demand of H2 at a time, how many cylinders it should order? For H2, Tc = 33 K, Pc = 12.8 bar. Vanderwaals constants are given by a = (27R2Tc2/64Pc) and b = (RTc/8Pc) where R = 0.08 lit.atm/gmol.oK. Use Vanderwaals equation for solving the problem.
46 A wet organic pigment 35% by weight of CCl4 is to be dried to 5%. The drier is to operate adiabatically with fresh plus recycle air entering the drier with 0.43 kg of CCl4/kg of dry air. The air leaves the drier with 0.945 kg of CCl4/kg of dry air. The capacity of the drier is 200 kg of bone dry solid/hr. Calculate the ratio of the recycled air to fresh air.
47 In a textile mill 20% by weight solution of caustic soda required for mercerization is prepared in the following way: First caustic soda is dissolved in correct quantity of water to produce 50% by weight of solution, cooled to remove all heat of dissolution and then diluted to 20% concentration with required quantity of water in the dilution tank. Evaluate the weight ratio of water added to dissolution tank and water flowing through the bypass line to dilution tank.
48 The reaction A à 2B + C takes place in a catalytic reactor (diagram is given below). The reactor effluent is sent to a separator. The overall conversion of A is 95%. The product stream from the separator consists of B, C and 0.5% of A entering the separator, while the recycle stream consists of the remainder of the unreacted A and 1% of B entering the separator. Calculate the single pass conversion of A in the reactor molar ratio of recycle to feed.
49 Air at 30oC and 150 kPa in a closed container is compressed and cooled. It is found that the first droplet of water condenses at 200 kPa and 15oC. Calculate the percent relative humidity of the original air. The vapor pressures of water at 15oC and 30oC are 1.7051 kPa and 4.246 kPa respectively.
50 Methanol vapor can be converted into formaldehyde by the following reaction scheme:
CH3OH + 0.5 O2 à HCHO + H2O

CH3OH à HCHO + H2

The fresh feed to the process was 0.5 kmol / hr of O2 and an excess methanol. All of the O2 reacts in the reactor. Formaldehyde and water are removed from the product stream first, after which H2 is removed from the recycled methanol. The recycle flow rate of methanol was 1 kmol/hr. The ratio of methanol reacting by decomposition to that by oxidation was 3. Draw the flow diagram and then calculate the per pass conversion of methanol in the reactor and the fresh feed rate of methanol.

51 A stock containing 1.526 kg moisture per kg dry solid is dried to 0.099 kg moisture per kg dry solid by countercurrent air flow. Fresh air entering contains 0.0152 kg water per kg dry sir and the exit air has 0.0526 kg water per kg dry air. What fraction of air is recycled if 52.5 kg of dry air flows per 1 kg of dry solid inside the drier?
An evaporator is fed continuously with 25 kg/hr of a solution which contains 10% NaCl, 10% NaOH and 80% H2O. During evaporation, H2O is removed from the solution and NaCl precipitates as crystals which is settled and removed. The concentrated liquor leaving the evaporator contains 50% NaOH, 2% NaCl and 48% H2O. Calculate
(i)Weight of salt precipitated per hour.
(ii) Weight of concentrated liquor leaving per hour

RITES Ltd Solved Model Placement Paper – Electronics

1. In a mercury arc rectifier

a. Ion stream moves from cathode to anode
b. Current flows from cathode to anode
c. Electron stream moves form anode to cathode
d. Ion stream moves from anode to cathode

2. For producing cathode spot in a mercury arc rectifier
a. An auxiliary electrode is used
b. Tube is evacuated
c. Low mercury vapour pressures are used
d. Anode is heated

3. If the voltage of anode B is raised to 510 V
a. Anode B will conduct but anode A will also continue to conduct
b. Anode B will not conduct but anode A will continue to conduct
c. Both anodes will not conduct
d. None of these

4. Ripple frequency of full wave rectifier working on 50 Hz supply will be
a. 25 Hz
b. 150 Hz
c. 6 anode rectifier with inter phase transformer
d. All will have identical power factor

5. The form factor for half-wave rectifier sine wave is
a. 1.05
b. 1.15
c. 1.45
d. 1.57

6. A silicon controlled rectifier is a
a. Unijuction device
b. Device with three junctions
c. Device with four junctions
d. None of the above

7. For full-wave rectifier sine wave, form factor is
a. 1.55
b. 1.44
c. 1.22
d. 1.11

8. At absolute zero temperature a semi-conductor behaves as
a. An Insulator
b. A Super-Conductor
c. A Good Conductor
d. A Variable Resistor

9. An electron in the conduction band
a. Has higher energy than the electron in the valence band
b. Has lower energy than the electron in the valence band
c. Loses its charge easily
d. Jumps to the top of the crystal

10. EG for silicon is 1.12 eV and for germanium is 0.72 eV thus it can be conducted that
a. More number of electron-hole pairs will be generated in silicon than in germanium at room temperature
b. Less number of electron hole pairs will be generated in silicon than in germanium at room temperature
c. Equal number of electron hole pairs will be generated in both at lower temperatures
d. Equal number of electron hole pairs will be generated in both at higher temperatures

11. Before doping semiconductor material is generally
a. Dehydrated
b. Heated
c. Hardened
d. Purified

12. Select the one that is a acceptor impurity element
a. Antimony
b. Gallium
c. Arsenic
d. Phosphorous

13. At room temperature when a voltage is applied to an intrinsic semiconductor
a. Most of the electrons and holes move towards negative terminal
b. Most of the electrons and holes move towards positive terminal
c. Electrons move towards positive terminal and holes towards negative terminal
d. Electrons move towards negative terminal and holes towards positive terminal

14. Under which of the following conditions avalanche breakdown in a semiconductor diode takes place ?
a. When potential barrier is reduced to zero
b. When reverse bias exceeds a certain value
c. When forward bias exceeds a certain value
d. When forward current exceeds a certain value

15. Select the rectifier that needs four diodes
a. Half wave rectifier
b. Center-tap full wave rectifier
c. Bridge rectifier
d. None of the above

16. Maximum forward current in case of signal diode is in the range of
a. 1A to 10A
b. 0.1A to 1A
c. Few milli amperes
d. Few nano amperes

17. In a semiconductor avalanche breakdown takes place when
a. Reverse bias exceeds the limiting value
b.Forward bias exceeds the limiting value
c. Forward current exceeds the limiting value
d. Potential barrier is reduced to zero

18. The D.C output from a power supply
a. Increases with higher values of filter capacitance and decreases with more load current
b. Decreases with higher values of filter capacitance and increases with more load current
c. Decreases with higher values of filter capacitance as well as with more load current
d. Increases with higher values of filter capacitance as well as with more load current

19. A solar cell provides a example of
a. Photo Voltaic Cell
b. Photo Conductive Cell
c. Photo Emissive Cell
d. Photo Radiation Cell

20. When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface, then it is expected that
a. No electrons are emitted
b. Hotons are emitted
c. Electrons of higher energy are emitted
d. Electrons of lower energy are emitted

21. An ideal diode should have
a. Zero resistance in the forward bias as well as reverse bias
b. Zero resistance in the forward bias and an infinitely large resistance in reverse bais
c. Infinitely large resistance in reverse bias
d. Infinitely large resistance in forward as well as reverse bais

22. The reverse resistance of a PN juction diode
a. Is always low
b. Is always high
c. Is given by breakdown voltage / reverse leakage current
d. Is given by forward voltage / reverse leakage current

23. In which case the temperature coefficient is positive
a. Intrinsic Semi-Conductor
b. Extrinsic Semi-Conductor
c. Both intrinsic as well as extrinsic semi-conductor
d. Neither intrinsic nor extrinsic semi-conductor

24. A PNP transistor is generally made of
a. Silicon
b. Germanium
c. Either silicon or germanium
d. None of the above

25. In a transistor the region that is very lightly doped and is very thin is
a. Emitter
b. Base
c. Collector
d. None of these

26. In a NPN transitor, when emitter junction is forward biased and collector junction is reverse biased, the transistor will operate in
a. Active Region
b. Saturated Region
c. Cut of Region
d. Inverted Region

27. A transistor will operate in inverted region if
a. Emitter junction is forward biased and collector junction is reverse biased
b. Emitter junction is reverse biased and collector junction is forward biased
c. Emitter junction as well as collector junction are forward biased
d. Emitter junction as well as collector junction are reverse biased

28. Which of the following is essential for transistor action ?
a. The base region must be very wide
b. The base region must be very narrow
c. The base region must be made of some insulating material
d. The collector region must be heavily doped

29. In a transistor, current ICBO flows when
a. Some D.C voltage is applied in the reverse direction to the emitter junction with the collector open circuited
b. Some D.C voltage is applied in the forward direction to the collector junction with the emitter open circuited
c. Some D.C voltage is applied in the reverse direction to the collector junction with the emitter open circuited
d. Some D.C voltage is applied in the forward direction to the emitter junction with the collector open circuited

30. The current Icbo
a. Increases with increase in temperature
b. Is normally greater for silicon transistors than germanium transistors
c. Mainly depends on the emitter base junction
d. Depends largely on the emitter doping

1 The problems 3-SAT and 2-SAT are
A) both in P
B) both NP-complete
C) NP-complete and in P respectively
D) undecidable and NP-complete respectively
Answer : (C)

2 Consider the following relation schema pertaining to a students database: Student (rollno, name, address) Enroll (rollno, courseno, coursename)
where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where ‘*’denotes natural join?
A) 8, 8
B) 120, 8
C) 960, 8
D) 960, 120
Answer : (C)

3 Consider a relation scheme R = (A, B, C, D, E, H) on which the following functional dependencies hold : (A -> B, BC -> D, E -> C, D -> A). What are the candidate keys of R?
A) AE, BE
B) AE, BE, DE
C) AEH, BEH, BCH
D) AEH, BEH, DEH
Answer : (D)

4 The goal of structured programming is to
A) have well indented programs
B) be able to infer the flow of control from the compiled code
C) be able to infer the flow of control from the program text
D) avoid the use of GOTO statements
Answer : (C)

5 The tightest lower bound on the number of comparisons, in the worst ease, for comparison-based sorting is of the order of
A) n
B) n 2
C) n log n
D) n log2 n
Answer : (B)

6 A circuit outputs a digit in the form of 4 bits. 0 is represented by 0000,1 by 0001,…, 9 by 1001. A combinational circuit is to be designed which takes these 4 bits as input and outputs 1 if the digit ³ 5, and 0 otherwise. If only AND, OR and NOT gates may be used, what is the minimum number of gates required
A) 2
B) 3
C) 4
D) 5
Answer : (C)

7 WA and B are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both A and B attempt to transmit a frame, collide, and A wins the first backoff race. At the end of this successful transmission by A, both A and B attempt to transmit and collide. The probability that A wins the second backoff race is
A) 0.5
B) 0.625
C) 0.75
D) 1.0
Answer : (A)

8 If 73x (in base-x number system) is equal to 54y (in base-y number system), the possible values of x and y are
A) 8, 16
B) 10, 12
C) 9, 13
D) 8, 11
Answer : (D)

9 In a packet switching network, packets are routed from source to destination along a single path having two intermediate nodes. If the message size is 24 bytes and each packet contains a header of 3 bytes, then the optimum packet size is
A) 4
B) 6
C) 7
D) 9
Answer : (D)

10 A Priority-Queue is implemented as a Max-Heap. Initially, it has 5 elements. The level-order traversal of the heap is given below: 10, 8,5,3,2 Two new elements 1 and 7 are inserted in the heap in that order. The level-order traversal of the heap after the insertion of the elements is
A) 10,8,7,5,3,2,1
B) 10,8,7,2,3,1,5
C) 10,8,7,1,2,3,5
D) 10,8,7,3,2,1,5
Answer : (D)

11 Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used is First Come First Served (FCFS). If FCFS is replaced by Shortest Seek Time First (SSTF), claimed by the vendor to give 50% better benchmark results, what is the expected improvement in the I/O performance of user programs ?
A) 50%
B) 40%
C) 25%br> D) 0%
Answer : (D)

12 How many distinct binary search trees can be created out of 4 distinct keys?
A) 5
B) 14
C) 24
D) 42
Answer : (B)
Q-13 Select the one true statement. A) Every binary tree is either complete or full.
B) Every complete binary tree is also a full binary tree.
C) Every full binary tree is also a complete binary tree
D) No binary tree is both complete and full.

Q-14 Which data structure has the fastest insertion procedure? A) Binary search tree
B) Ordered array
C) Heap
D) Unordered linked list
E) Ordered linked list

Q-15 What are the complexities of the insert, remove and search methods of a binary search tree in the worst case? A) insert is O(n), remove is O(n), search is O(n)
B) insert is O(log n), remove is O(log n), search is O(n)
C) insert is O(log n), remove is O(log n), search is O(log n)
D) insert is O(log n), remove is O(log n), search is O(1)
E) These methods can’t be defined on a binary search tree

Q-16 This Ethernet frame type is characterized by its use of the code AA in the SAP fields. A) Ethernet II
B) Ethernet RAW
C) Ethernet 802.2
D) Ethernet SNAP

Q-17 Which of the following are examples of routed protocols? (Choose all that apply) A) IP
B) IPX
C) RIP
D) OSPF
E) AppleTalk

Q-18 If switches are used to replace hubs on a network, which of the following statements is true? A) The number of broadcast domains will decrease
B) The number of collision domains will increase
C) The number of collision domains will decrease
D) The number of broadcast domains will be zero

Q-19 Full duplex Ethernet communication is only possible when:

A. Systems are connected to same LAN segments
B. Systems are connected to a bridged ports
C. Systems are connected to their own switch port
D. Systems are running over a fiber optic connection

Q-20 SQL is the combination of

A ) DDL and DQL
B ) DDL , DML and DQL
C ) DDL,DML,DQL and DCL
D ) None of these

Q-21 Which of the following applications may use a stack?

A) A parentheses balancing program.
B) Keeping track of local variables at run time.
C) Syntax analyzer for a compiler.
D) All of the above

Q -22 Consider the implementation of the Stack using a partially-filled array. What goes wrong if we try to store the top of the Stack at location [0] and the bottom of the Stack at the last used position of the array?

A) Both peek and pop would require linear time.
B) Both push and pop would require linear time.
C) The Stack could not be used to check balanced parentheses.
D) The Stack could not be used to evaluate postfix expressions.

Q-23 Select the one true statement.
A) Every binary tree is either complete or full.
B) Every complete binary tree is also a full binary tree.
C) Every full binary tree is also a complete binary tree
D) No binary tree is both complete and full.

Q-24 Which data structure has the fastest insertion procedure? A) Binary search tree
B) Ordered array
C) Heap
D) Unordered linked list
E) Ordered linked list

Q-25 What are the complexities of the insert, remove and search methods of a binary search tree in the worst case? A) insert is O(n), remove is O(n), search is O(n)
B) insert is O(log n), remove is O(log n), search is O(n)
C) insert is O(log n), remove is O(log n), search is O(log n)
D) insert is O(log n), remove is O(log n), search is O(1)
E) These methods can’t be defined on a binary search tree

Q-26 This Ethernet frame type is characterized by its use of the code AA in the SAP fields.
A) Ethernet II
B) Ethernet RAW
C) Ethernet 802.2
D) Ethernet SNAP

Q-27 Which of the following are examples of routed protocols? (Choose all that apply) A) IP
B) IPX
C) RIP
D) OSPF
E) AppleTalk

Q-28 If switches are used to replace hubs on a network, which of the following statements is true? A) The number of broadcast domains will decrease
B) The number of collision domains will increase
C) The number of collision domains will decrease
D) The number of broadcast domains will be zero

Q-29 Full duplex Ethernet communication is only possible when:

A. Systems are connected to same LAN segments
B. Systems are connected to a bridged ports
C. Systems are connected to their own switch port
D. Systems are running over a fiber optic connection

Q-30 SQL is the combination of

A ) DDL and DQL
B ) DDL , DML and DQL
C ) DDL,DML,DQL and DCL
D ) None of these

Q-31 Which of the following applications may use a stack?

A) A parentheses balancing program.
B) Keeping track of local variables at run time.
C) Syntax analyzer for a compiler.
D) All of the above

Q -32 Consider the implementation of the Stack using a partially-filled array. What goes wrong if we try to store the top of the Stack at location [0] and the bottom of the Stack at the last used position of the array?

A) Both peek and pop would require linear time.
B) Both push and pop would require linear time.
C) The Stack could not be used to check balanced parentheses.
D) The Stack could not be used to evaluate postfix expressions.