RITESLtd Electronics-Communication-Engineering-ECE Contributed by Maya Murali updated on Jun 2019

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