RTU 2016 Question Paper Semester IV Electrical and Electronics Engineering Electrical Measurements

TotalNo of Pages:fl

Examl June-July 2016
B.Tech. IV'Sem (Main & Back)
Electrical & Electronics Engineering
4EX3A Electrical Measurements
Common with EE, EX, EI
Maximum Marks: 80
Time: 3 Hours 26
Min. Passing Marks (Main & Back):
24
Min. Passing Marks (Old Back):

Instructions to Candidates :'

Attemptanyftvequestions,selectingonequestionfromeachunit.All
QuestionsCarryequalmarks.schematicdiagram;rnustbeshown
.wherevernecessary.Anydatayoufeelmissingsuitablybeassumedand
staled clearlY'
[Jnitsofquantitiesused/calculatedmustbeStatedclearly.
UseoJ,followingsupportingmaterialispermittedduringexamination.
(Mentioned in form No'205)
:' NIL
t. NtL
- I]NIT.I
t8l
errors in moving iron instruments'
Q' 1 (a) Discuss the different types of
v.
of single phase energy meter by phantom
(b) Explain the testing and calibration
t8l
loading.

OR
iron
Q.1(a)Describetheworkingandconstructionaldetailsofanattractiontypemoving
t8l
instrument'
of the elrors in wattmeter' t8l
(b) Discuss the comPensation and adjustment
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[10s00]
l4E4r22l

UNIT.II
Q2 Draw the equivalent circuit and phasor diagram of a current transformer. Also derive
the expressions for ratio and phase angle effors. t16]

OR

Q.2 (a) Discuss the measurement of power by two-wattmeter method. [8+8=16]

(b) Explain the effect of the following on the performance of current transformers.

(i) Change of primary winding current

(ii) Change of secondary circuit burden
(iii) Change of frequency

Q.3 (a) Describe the basic principle of operation of d.c. potentiometer. Explain why a
potentiometer does not load the voltage source whose voltage is being

determined. . t8l

(b) Explain the term 'standardization' of a potentiometer. Describe the procedure of
standardization of a d.c. potentiometer. t8l

qR

Q.3 (a) Draw the circuit diagram of a Crompton's potentiometer and explain its working.
Describe the steps used when measuring an unknown resistance. t8l

(b) What is a volt-ratio box? Explain its construction, Working and applications. l8l

14841221 Page? of 4 [10s001

Q.4 (a) A Wheatstone bridge is shown in figure t6l

P =7kdl
R=lko
S=5kO
G = 100Q

The thevenin source generator voltage Eo = 24mY and the galvanometer current
is 13.6 pA. Calculate the value of Q
(b) Describe the substitution method of measurement of medium.resistances. List the
factors on which the accuracy of the methods depends. t10l
OR
Q.4 (a) What are the different difficulties encountered in the measurement of high
resistances? Explain how these difficulties are overcome. tSl
(b) What is the importance of the value of earth's resistance. What are the fhctors
which influence its value. l8l

UNIT-V
Q.5 (a) The four impedances of AC Bridge are 21 = 400L50" A; Zz = 2A0L4A' A;
Zz = 800L-50o O; Zq = 4O0 QLIO" Q; here Zr, Zzin one arm and Zj, Za, in

another arm of bridge.

Find out whether the bridge is balanced under these conditions or not. t6l

l4E4L22l Page 3 of4 [10s001

,.e.asured with the
helP of
^- tr-a
can be measut
caPacitance
an unknown are theY
(b) Describe how of this bridge and how
bridge' What are the limitations tl0l
D'sautY's
overcome'
B in figure'
t6l
is shown
comparison bridge
A Maxwell's inductance
Q.5 (a)
b

L,,r,\ | / 100fi

resistance of
ArmabconsistsofacoilwithinductanceLl&resist&flCeflinserieswithanon-
are each a non- inductive
and ad
R' Arm bc
inductive resistance
resistance &
& R = 1'36Q' Fine the
l00o.ArmadconsistsofstandardvariableinductorLofresistarce32,T{L.
when I 2 = 47'8MH
Balance is obtained
the coil in arm
ab' ation of
inductance of

(b) Explain how wien, ":i:]::,":;-Til;"rfrT:']J1"ffiters r10r
the exPressron
frequencY' Derive

t10so0l
Page 4 of 4
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