Software Engineering - 50 Obejective Ques & Ans

Q.1 The most important feature of spiral model is
(A) requirement analysis. (B) risk management.
(C) quality management. (D) configuration management.
Ans: B
Q.2 The worst type of coupling is
(A) Data coupling. (B) control coupling.
(C) stamp coupling. (D) content coupling.
Ans: D
Q.3 IEEE 830-1993 is a IEEE recommended standard for
(A) Software requirement specification.
(B) Software design.
(C) Testing.
(D) Both (A) and (B)
Ans: A
Q.4 One of the fault base testing techniques is
(A) unit testing. (B) beta testing.
(C) Stress testing. (D) mutation testing.
Ans: D
Q.5 Changes made to an information system to add the desired but not necessarily the
required features is called
(A) Preventative maintenance.
(B) Adaptive maintenance.
(C) Corrective maintenance.
(D) Perfective maintenance.
Ans: D
Q.6 All the modules of the system are integrated and tested as complete system in the
case of
(A) Bottom up testing (B) Top-down testing
(C) Sandwich testing (D) Big-Bang testing
Ans: D
Q.7 If every requirement stated in the Software Requirement Specification (SRS) has
only one interpretation, SRS is said to be
(A) correct. (B) unambiguous.
(C) consistent. (D) verifiable.
Ans: B
Q.8 A fault simulation testing technique is
(A) Mutation testing (B) Stress testing
(C) Black box testing (D) White box testing
Ans: A
Q.9 Modules X and Y operate on the same input and output data, then the cohesion is
(A) Sequential (B) Communicational
(C) Procedural (D) Logical
Ans: B
Q.10 If the objects focus on the problem domain, then we are concerned with
(A) Object Oriented Analysis.
(B) Object Oriented Design
(C) Object Oriented Analysis & Design
(D) None of the above
Ans: A
Q.11 SRS is also known as specification of
(A) White box testing (B) Stress testing
(C) Integrated testing (D) Black box testing
Ans: D
Q.12 The model in which the requirements are implemented by category is
(A) Evolutionary Development Model
(B) Waterfall Model
(C) Prototyping
(D) Iterative Enhancement Model
Ans: A
Q.13 SRD stands for
(A) Software requirements definition
(B) Structured requirements definition
(C) Software requirements diagram
(D) Structured requirements diagram
Ans: B
Q.14 A COCOMO model is
(A) Common Cost Estimation Model.
(B) Constructive Cost Estimation Model.
(C) Complete Cost Estimation Model.
(D) Comprehensive Cost Estimation Model.
Ans: B
Q.15 Which of the following statements is true
(A) Abstract data types are the same as classes
(B) Abstract data types do not allow inheritance
(C) Classes cannot inherit from the same base class
(D) Object have state and behavior
Ans: B
Q.16 The desired level of coupling is
(A) No coupling (B) Control coupling
(C) Common coupling (D) Data coupling
Ans: D
Q.17 In the spiral model ‘risk analysis’ is performed
(A) In the first loop (B) in the first and second loop
(C) In every loop (D) before using spiral model
Ans: C
Q.18 For a well understood data processing application it is best to use
(A) The waterfall model (B) prototyping model
(C) the evolutionary model (D) the spiral model
Ans: A
Q.19 Coupling and cohesion can be represented using a
(A) cause-effect graph (B) dependence matrix
(C) Structure chart (D) SRS
Ans: B
Q.20 The symbol represents
(A) mandatory 1 cardinality (B) mandatory many cardinality
(C) optional 0 or 1 cardinality (D) optional zero-many cardinality
Ans: D
Q.21 Each time a defect gets detected and fixed, the reliability of a software product
(A) increases. (B) decreases.
(C) remains constant. (D) cannot say anything.
Ans: A
Q.22 Output comparators are used in
(A) static testing of single module
(B) dynamic testing of single module
(C) static testing of single and multiple module
(D) dynamic testing of single and multiple module
Ans: D
Q.23 The feature of the object oriented paradigm which helps code reuse is
(A) object. (B) class.
(C) inheritance. (D) aggregation.
Ans: C
Q.24 The level at which the software uses scarce resources is
(A) reliability (B) efficiency
(C) portability (D) all of the above
Ans: B
Q.25 If every requirement can be checked by a cost-effective process, then the SRS is
(A) verifiable (B) traceable
(C) modifiable (D) complete
Ans: A
Q.26 Modifying the software to match changes in the ever changing environment is called
(A) adaptive maintenance (B) corrective maintenance
(C) perfective maintenance (D) preventive maintenance
Ans: A
Q.27 All activities lying on critical path have slack time equal to
(A) 0 (B) 1
(C) 2 (D) None of above
Ans: A
Q.28 Alpha and Beta Testing are forms of
(A) Acceptance testing (B) Integration testing
(C) System Testing (D) Unit testing
Ans: A
Q.29 An object encapsulates
(A) Data (B) Behaviour
(C) State (D) Both Data and behaviour
Ans: D
Q.30 In function point analysis, number of general system characteristics used to rate the
system are
(A) 10 (B) 14
(C) 20 (D) 12
Ans: B
Q.31 Aggregation represents
(A) is_a relationship (B) part_of relationship
(C) composed_of relationship (D) none of above
Ans: C
Q.32 If P is risk probability, L is loss, then Risk Exposure (RE) is computed as
(A) RE = P/L (B) RE = P + L
(C) RE = P*L (D) RE = 2* P *L
Ans: C
Q.33 Number of clauses used in ISO 9001 to specify quality system requirements are:
(A) 15 (B) 20
(C) 25 (D) 28
Ans: B
Q.34 ER model shows the
(A) Static view. (B) Functional view.
(C) Dynamic view. (D) All the above.
Ans: A
Q.35 The tools that support different stages of software development life cycle are called:
(A) CASE Tools (B) CAME tools
(C) CAQE tools (D) CARE tools
Ans: A
Q.36 Changes made to the system to reduce the future system failure chances is called
(A) Preventive Maintenance (B) Adaptive Maintenance
(C) Corrective Maintenance (D) Perfective Maintenance
Ans: A
Q.37 Requirements can be refined using
(A) The waterfall model (B) prototyping model
(C) the evolutionary model (D) the spiral model
Ans: B
Q.38 The model that assumes that effort and development time are functions of product
size alone is
(A) Basic COCOMO model (B) Intermediate COCOMO model
(C) Detailed COCOMO model (D) All the three COCOMO models
Ans: A
Q.39 Structured charts are a product of
(A) requirements gathering (B) requirements analysis
(C) design (D) coding
Ans: C
Q.40 The problem that threatens the success of a project but which has not yet happened is
a
(A) bug (B) error
(C) risk (D) failure
Ans: C
Q.41 The main purpose of integration testing is to find
(A) design errors (B) analysis errors
(C) procedure errors (D) interface errors
Ans: D
Q.42 Pseudocode can replace
(A) flowcharts (B) structure charts
(C) decision tables (D) cause-effect graphs
Ans: A
Q.43 If a program in its functioning has not met user requirements is some way, then it is
(A) an error. (B) a failure.
(C) a fault. (D) a defect.
Ans: D
Q.44 The testing that focuses on the variables is called
(A) black box testing (B) white box testing
(C) data variable testing (D) data flow testing
Ans: A
Q.45 CASE Tool is
(A) Computer Aided Software Engineering
(B) Component Aided Software Engineering
(C) Constructive Aided Software Engineering
(D) Computer Analysis Software Engineering
Ans: A
Q.46 Software consists of
(A) Set of instructions + operating procedures
(B) Programs + documentation + operating procedures
(C) Programs + hardware manuals
(D) Set of programs
Ans: B
Q.47 Which is the most important feature of spiral model?
(A) Quality management (B) Risk management
(C) Performance management (D) Efficiency management
Ans: B
Q.48 Which phase is not available in software life cycle?
(A) Coding (B) Testing
(C) Maintenance (D) Abstraction
Ans: D
Q.49 Which is not a step of requirement engineering?
(A) Requirements elicitation (B) Requirements analysis
(C) Requirements design (D) Requirements documentation
Ans: C
Q.50 FAST stands for
(A) Functional Application Specification Technique
(B) Fast Application Specification Technique
(C) Facilitated Application Specification Technique
(D) None of the above
Ans: C

Q&A: Electrical Machines_Part 1

1.   What is the function of carbon brush used in D.C generator?
The function of carbon brush is to collect current from the commutator and supply is to the external load circuit and to the field circuit.

2.    Distinguish between lap winding and wave winding used in dc machine
      Lap winding is designed for high current and low voltage machines.
     Wave winding is designed for low current and high voltages.

3.    Write the number of parallel paths in a lap and wave connected windings
In a lap wound machine, the number of parallel paths is equal to the number of poles. But in wave wound machine, the number of parallel paths is always two irrespective of number of poles.

4.    Name the three things required for the generation of emf
o    Presence of armature conductors
o    Presence of magnetic field
o    Relative motion between conductor and magnetic field

5. Define slip of induction motor?
        Slip is descriptive of the way in which the rotor slips back from synchronism. It is usually expressed as percentage of synchronous speed.

6.    What is meant by self excited and separately excited dc generator
•    Self-excited generator are those whose field magnets are energized by the current produced by the generator themselves
•    Separately excited generator are those whose field magnets are energized from an independent external source of dc current

7.    What is the basic difference between dc generator and dc motor
Generator converts mechanical energy into electrical energy. Motor converts electrical energy into mechanical energy. But there is no constructional difference between the two.

8.    Write down the emf equation of dc generator. Give the meaning of each symbol
Emf induced E=?ZNP/60A
?=flux per pole in Weber
Z=total number of armature conductors
N=speed of armature in rpm
P=number of poles
A=number of parallel paths

9.what is pole pitch?
        The periphery of the armature is divided for a number of poles of the generator. the center to center distance between two adjacent poles is called pole pitch
        It is also equal to the number of armature slots or armature conductors per pole.

10.How can the voltage in a DC generator be increased?
                    Increasing the main field flux and the speed of the armature      can increase the voltage in a DC generator.

11.What is critical resistance of a DC shunt generator?
           The value of resistance of shunt field winding beyond which the shunt generator fails to build up its voltage is known as “ critical resistance “.

12.what are the conditions to be fulfilled for a shunt generator to build up Voltage?
a)    There must be some residual magnetism in the field poles.
b)    The shunt field resistance should be less than critical resistance.
c)    The field coils should be connected with the armature in such a way that current flowing through them should increase the EMF induced by the residual magnetism.

13.What do you mean by residual flux in DC generator.
        The magnetic flux retained in the poles of the machine even without field supply is called the residual flux.

14.A DC generator fails to self excite. . List the cause for the failure for the failure.
a)    Residual magnetism may not there in the poles.
b)    Direction of rotation may be wrong.
c)    The field resistance may be more than critical resistance.
d)     There may be disconnection in the field winding.
e)    Brush contact may be poor.
f)    The field coils may be connected with the armature to oppose the EMF due to residual magnetism.

15.What are open circuit characteristics of DC shunt generator.
        It is the relation between the field current and the emf induced in the armature

16. Why a 3-phase synchronous motor will always run at synchronous speed?
                  Because of the magnetic coupling between the stator poles and rotor poles the motor runs exactly at synchronous speed.

17. Mention the methods of starting of 3-phase synchronous motor.
            a.   A D.C motor coupled to the synchronous motor shaft.
            b.     A small induction motor coupled to its shaft.
            c.    Using damper windings as a squirrel cage induction motor.

18.What are the principal advantages of rotating field system type of construction of synchronous machines?
•    Form Stationary connection between external circuit and system of conditions enable the machine to handle large amount of volt-ampere as high as 500 MVA.
•    The relatively small amount of power required for field system can be easily supplied to the rotating field system via slip rings and brushes.
•    More space is available in the stator part of the machine for providing more insulation to the system of conductors.
•    Insulation to stationary system of conductors is not subjected to mechanical stresses due to centrifugal action.
•    Stationary system of conductors can easily be braced to prevent deformation.
•    It is easy to provide cooling arrangement.

19.Write down the equation for frequency of emf induced in an alternator.
       F    = PN / 120 Hertz
Where P    = No. Of poles
           N    = Speed in rpm.

20.What are the advantages of salient pole type of construction used for synchronous machines?
•    They allow better ventilation.
•    The pole faces are so shaped radial air gap length increases from the pole center to the pole tips so that flux distribution in the air gap is sinusoidal in shape which will help to generate sinusoidal emf.
•    Due the variable reluctance, the machine develops additional reluctance power, which is independent of excitation.

21Why do cylindrical rotor alternators operate with steam turbines?
     Steam turbines are found to operate at fairly good efficiency only at high speeds. The high-speed operation of rotor tends to increase mechanical losses, so the rotors should have smooth external surface. Hence smooth cylindrical type rotors with less diameter and large axial length are used for synchronous generators driven by steam turbines with either 2 or 4 poles.

22.Which type of synchronous generators are used in Hydroelectric plants and why?
As the speed of operation is low, for hydro turbines used in hydroelectric plants, salient pole type synchronous generators are used. These allow better ventilation and also have other advantages over smooth cylindrical type rotor.

23.What is the relation between electrical degree and mechanical degree?
Electrical degree ?e and mechanical degree are related to one another by the number of poles P, the electrical machine has, as given by the following equation.
?e = (P/2) ?m

24. What is the meaning of electrical degree?
Electrical degree is used to account the angle between two points in rotating electrical machines. Since all electrical machines operate with the help of magnetic fields, the electrical degree is accounted with reference to the polarity of magnetic fields. 180 electrical degrees is accounted as the angle between adjacent North and South poles

25. Why short-pitch winding is preferred over full pitch winding?
Advantages: -
•    Waveform of the emf can be approximately made to a sine wave and distorting harmonics can be reduced or totally eliminated.
•    Conductor material, copper is saved in the back and front-end connections due to less coil span.
•    Fractional slot winding with fractional number of slots/phase can be used which in turn reduces the tooth ripples.
•    Mechanical strength of the coil is increased.

  
26. Write down the formula for distribution factor.
Kd = sin (mß/2)    or     Kdn = sin (mnß/2)
          msin(ß/2)                 msin(nß/2)
where
        m    - number of slots/pole/phase
        ß    - angle between adjacent slots  in electrical degree
        n    - order of harmonics.

27. Define winding factor.
    The winding factor Kw is defined as the ratio of phasor addition of emf induced in all the coils belonging to each phase winding of their arithmetic addition.   

28. Why are alternators rated in kVA and not in kW?
    The continuous power rating of any machine is generally defined as the power the machine or apparatus can deliver for a continuous period so that the losses incurred in the machine gives rise to a steady temperature rise not exceeding the limit prescribed by the insulation class.
    Apart from the constant loss the variable loss incurred in alternators is the copper loss, occurring in the 3-phase winding, which depends on I2R, the square of the current delivered by the generator. As the current is directly related to apparent power delivered by the generator, the alternators have only their apparent power in VA/kVA/MVA as their power rating

29. What are the causes of changes in voltage of alternators when loaded?
•    Voltage variation due to the resistance of the winding R.
•    Voltage variation due to the leakage reactance of the winding X1.
•    Voltage variation due to the armature reaction.

30. What is meant by armature reaction in alternators?
  The interaction between flux set up by the current carrying armature conductors   and the main field flux   is defined as the armature reaction.

31.  What do you mean by synchronous reactance?
    It is the sum of the leakage reactance X1 and armature reactance Xa 
        Xs = X1 + Xa

32. What is synchronous impedance?
The complex addition of resistance R and synchronous reactance jXs is synchronous impedance Zs.
Zs = (R+jXs)    = Zs??
Where ? = tan –1(Xs/R)
|Zs| = v(R2+jXs2)   

33. What is meant by load angle of an alternator?
    The phase angle introduced between the induced emf phasor E and terminal voltage phasor V during the load condition of an alternator is called load angle. The load angle increases with increase in load. It is positive during generator operation and negative during motor operation.
 

34. Define the term voltage regulation of alternator.
    It is defined as the change in terminal voltage from no load-to-load condition expressed as a function or terminal voltage at load condition, the speed and excitation conditions remaining same.
% Regulation = (E-V)/V x 100

35. What is the necessity for predetermination of voltage regulation?
    Most of the alternators are manufactured with large power rating and large voltage ratings. Conduction load test is not possible for such alternators. Hence other indirect methods of testing are used and the performance can be predetermined at any desired load currents and power factors.

36. Why is the synchronous impedance method of estimating voltage regulation is considered as pessimistic method?
    Compared to other methods, the value of voltage regulation obtained by this method is always higher than the actual value and therefore is called pessimistic method.

37. Why is the MMF method of estimating the voltage regulation is considered as the optimization method?
    Compared to EMF method, MMF method involves more number of complex calculation steps. Further the OCC is referred twice and SCC is referred once while predetermining the voltage regulation for each load condition. Reference of OCC takes core saturation effect. As this method requires more effort, the final result is very close to the actual value. Hence this method is called the optimistic method.

38.What does hunting of synchronous motor mean?
   When the load applied to the synchronous motor is suddenly increased or decreased, the rotor oscillates about its synchronous position with respect to the stator field.  This action is called hunting.

39.What could be the reasons if a 3-phase synchronous motor fails to start?
                   It is usually due to the following reasons
              a.  Voltage may be too low.
              b.  Too much starting load.
              c.  Open circuit in one phase or short circuit.
              d.  Field excitation may be excessive

40. What is synchronous condenser?
                     An over-excited synchronous motor used for the improvement of power factor is called as synchronous condenser because, like a capacitor it takes a leading current.

41.Write the applications of synchronous motor.
               a.  Used for power factor improvement in sub-stations and in industries.
               b.  Used in industries for power applications.
               c.  Used for constant speed drives such as motor-generator set, pumps and compressors.

42. What is an inverted 'V' curve?
                   For a constant load, if the power factor is plotted against various values of field exciting current, the curve formed is known as inverted 'V' curve.

43. How the synchronous motor is made self-starting?
                   By providing damper windings in the pole faces, it will start and run like a squirrel cage induction motor.

44.  Asynchronous motor starts as usual but fails to develop its full torque.  What could it be due to?
               a.  Exciter voltage may be too low.
               b.  Field spool may be reversed.
               c.  There may be either open-circuit or short-circuit in the field.          

45.What are the two types of 3-phase induction motor?
a.    Squirrel cage induction motor.
b.    Slip ring induction motor.

46.Write the two extra features of slip ring induction motors.
a.    Rotor is having 3-phase winding.
b.    Extra resistance can be added in the rotor circuit for improving in the power factor with the help of three slip rings.

47.Can we add extra resistance in series with squirrel cage rotor? State the reason?
        We cannot add extra resistance in series with the rotor because all the copper bars of the rotor are short circuited in both the sides by copper end rings to have a closed circuit.

48.Why an induction motor is called rotating transformer?
        The rotor receives electrical power in exactly the same way as the secondary of a two winding transformer receiving its power from primary. That is why an induction motor can be called as a rotating transformer i.e., in which primary winding is stationary but the secondary is free to rotate.

     49.Why an induction motor will never run at its synchronous speed?
        If it runs at synchronous speed then there would be no related speed between the two, hence no rotor emf, no rotor current so no rotor torques to maintain rotation. That is why the rotor runs at its synchronous speed.

      50.What are slip rings?
        The slip rings are made of copper alloys and are fixed around the shaft insulating it. Through these slip rings and brushes the rotor winding can be connected to external circuits.

     51.State the difference between slip ring rotor and cage rotor of an induction motor?
        Slip ring rotor has 3-phase windings. Three ends of which are stared and the other three ends are brought up and connected to 3 slip rings mounted in the shaft. Extra resistance can be added in the rotor circuit. Squirrel cage rotor has short-circuited copper bars.  Extra resistance can’t be added as slip ring rotor.

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