Electrical Engineering - Electrical and Electronic Measurement
Exam Duration: 45 Mins Total Questions : 30
The current flowing in a resistor of 1Ω is measured to be 25A.But it was discovered that ammeter reading was low by 15 and resistance was maked high by 0.5%.Find true power as percentage of original power
- (a)
95%
- (b)
100.1%
- (c)
101.%
- (d)
102.4%
A 0-200V voltmeter has a guaranteed accuracy of 1% of full scale reading.The voltage measured by this instrument is 100V.Calculate the limiting error i percent
- (a)
4
- (b)
2.5
- (c)
2
- (d)
1
Eddy current damping can be used for moving iron instrument because
- (a)
Weight of the instrument will increase
- (b)
presence of permanent magnet required for this purpose will affect the deflection and the instrument reading
- (c)
size of instrument will increase
- (d)
eddy current will passthrough the iron and thereby cause loss
The scale of a dynamometer type instrument marked in 'terms of rms value would be
- (a)
uniform through out
- (b)
non-uniform crowded near full scale
- (c)
non-uniform crowded at the beginning
- (d)
non-uniform crowded around mid scale
An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. If a stray DC magnetic field having a component along the axis of the meter coil appears, the meter reading would be
- (a)
unaffected
- (b)
decreased
- (c)
increased
- (d)
either decreased or increased depending on the direction of the DC field
An advantage of a permanent magnet moving coil instrument is that ·t is
- (a)
free from friction error
- (b)
has high (torque/weight of the moving parts) ratio
- (c)
has low (torque/weight of the moving parts) ratio
- (d)
can be used on both AC and DC
The minimum number of wattmeter(s) required to measure 3-phase, 3 wire balanced or unbalanced power is
- (a)
1
- (b)
2
- (c)
3
- (d)
4
The coils having self inductance of 10 mH and 15 mH have an effective inductance of 40 mH, when connected in series aiding. What will be the equivalent inductance, if we connect them in series opposing?
- (a)
20 mH
- (b)
10 mH
- (c)
5 mH
- (d)
zero
In the Owen's bridge shown in below figure, Z1=200ㄥ600, Z2=400ㄥ-900, Z3=300ㄥ00, Z4=400ㄥ300.Then, choose the correct statement.
- (a)
Bridge is balanced with given impedance values
- (b)
Bridge can be balanced, if Z4=600ㄥ600
- (c)
Bridge can be balanced, if Z3=400ㄥ00
- (d)
Bridge can not be balanced with given configuration
In the single-phase induction meter, in order to obtain true value of energy, the shunt magnetic flux should lag behind the applied voltage by
- (a)
90°
- (b)
00
- (c)
450
- (d)
None of these
Fluid friction damping can be used in
- (a)
horizontally mounted instrument
- (b)
vertically mounted instrument
- (c)
both in horizontally and vertically mounted instrument
- (d)
None of the above
In this measurement of 3-phase power by 2-wattmeter method, if the 2 wattmeter reading are equal, the power factor of the circuit is
- (a)
0.8 lagging
- (b)
0.8 leading
- (c)
zero
- (d)
unity
The meter constant of a single-phase, 230 V induction wattmeter is 600 rev/kW-h.The speed of the meter disc for current of 15 A at 0.8 power factor lagging will be
- (a)
30.3rpm
- (b)
25.02rpm
- (c)
27.6rpm
- (d)
33.1rpm
The scale of a voltmeter is uniform. Its type is
- (a)
moving iron
- (b)
induction
- (c)
moving coil permanent magnet
- (d)
moving coil dynamometer
A transfer instrument employed in the standardization of a polar type AC potentiometer is
- (a)
an electrostatic instrument
- (b)
a thermal instrument
- (c)
a dynamometer instrument
- (d)
a moving coil instrument
A moving coil galvanometer is made into a DC ammeter by connecting
- (a)
a low resistance across the meter
- (b)
a high resistance in series with the meter
- (c)
a pure inductance across the meter
- (d)
a capacitor in series with the meter
The two inputs of a CRO are fed with two stationary periodic signals. In the X-Y mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this.
- (a)
The signals are not sinusoidal
- (b)
The amplitudes of the signals are very close but not equal
- (c)
The signals are sinusoidal with their frequencies very close but not equal
- (d)
There is a constant but small phase difference between the signals
The operation of megger is based on
- (a)
dynamometer
- (b)
electrostatic meter
- (c)
moving coil meter
- (d)
moving iron meter
What is the velocity of electrons that have been accelerated through a potential of 2000 V?
- (a)
2x 106 m/s
- (b)
2.65 x 107 rn/s
- (c)
1.65 x107 m/s
- (d)
2.65 x 106 rn/s
Match the list I with List II and select the correct answer using the codes given below the lists.
| List I | List II |
|---|---|
| P.Wien's bridge | 1.Measurement of resistance` |
| Q.Maxwell's bridge | 2.High q inductors |
| R.schering's bridge | 3.Measurement of frequency |
| S.Anderson's bridge | 4.High voltage capacitors |
| T.Blumbeim's bridge | 5.Low Q inductors |
| 6.Insensitive to stray electrostatic fields |
- (a)
P Q R S T 3 5 4 3 6 - (b)
P Q R S T 5 4 4 6 1 - (c)
P Q R S T 6 4 5 6 3 - (d)
P Q R S T 4 5 3 6 1
A DC potentiometer is designed to measure up to about 2 V with a slide wire of 300 mm. A standard cell of emf 1.18 V obtains balance at 600 mm. A test cell is seen to obtain balance at 680 mm. The emf of the test cell is
- (a)
1.00V
- (b)
1.34V
- (c)
1.50V
- (d)
1.70V
A recorder
- (a)
is an indicating instrument which displays a time varying signal
- (b)
is a device whose function is to record the value of quantity as it is being measured
- (c)
records electrical and non-electrical quantities as a function of time or relates two signals to each other
- (d)
Both (b) and (c)
A 50 Hz voltage is measured with a moving iron voltmeter and a rectifier type AC voltmeter connected in parallel. If the meter readings are V, and V2 respectively and the meters are free from cal ibration errors, then the form factor of the AC voltage may be estimated as
- (a)
\(V_1\over V_2\)
- (b)
\(1.11V_1\over V_2\)
- (c)
\(\sqrt{2}V_1\over V_2\)
- (d)
\(\pi V_1\over V_2\)
The circuit of figure gives a triangular output. The frequency of the output wave will be
- (a)
41.7Hz
- (b)
50Hz
- (c)
60Hz
- (d)
61.7Hz
The simultaneous applications of signals x(t) and y(t) to the horizontal and vertical plates respectively, of an oscilloscope, produces a vertical figure of 8 display. If P nd Q are constants and x(t) = P sin (4t + 30), then y(t) is equal to
- (a)
Qsin(4t-30)
- (b)
Qsin(2t+15)
- (c)
Qsin(8t+60)
- (d)
Qsin(4t+30)
The set-up in figure is used to measure resistance R.The ammeter and voltmeter resistance are 0.01Ω and 2000Ω respectively. Their readings are 2 A and 180 V respectively, giving a measured resistance of 90Ω. The percentage error in the measurement is
- (a)
2.25%
- (b)
2.35%
- (c)
4.5%
- (d)
4.71%
Two sinusoidal signals p(ω1t) =A sinω1t and q(ω1t) are applied to X and Y inputs of a dual channel CRO.The Lissajaus figure displayed on the screen is shown below
The signal q(ω2 t) will be represented as
- (a)
q(ω2t) =A sin ω2t, ω2 =2ω1
- (b)
q(ω2t)=A sin ω2t, ω2=\(={ω_1\over 2}\)
- (c)
q(ω2t)=A cos ω2t, ω2=2ω1
- (d)
1(ω2t)=A cos ω2t, ω2=\(\omega_1\over2\)
The figure shows a three-phase, delta connected load supplied from a 400 V, 50 Hz, 3-phase balanced source. The PressureCoil (PC) and Current Coil (CC) of a wattmeter are connected to the load as shown, with the coiI polarities suitably selected to ensurea positive deflection. The wattmeter reading will be
- (a)
zero
- (b)
1600W
- (c)
800W
- (d)
400W
A voltmeter has a sensitivity of 1000 ON reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA.The actual resistance of the unknown resistor will be
- (a)
20kΩ
- (b)
18.57kΩ
- (c)
Either (a) or (c)
- (d)
21.43kΩ
A resistance R is measured using the connection shown in below figure.
The current measured is 10 A on range 100 A and the voltage measured is 125 V on 150 V range. The scales of the ammeter and voltmeter are uniform. The total number of scale divisions of ammeter is 100 and of volt meter is 150. The scale division can be distinguished. The constructional error of the ammeter is ± 0.3% and that of voltmeter ± 0.4%. The resistance of the ammeter is 0.25Ω.The value of R is
- (a)
12.5
- (b)
12.25
- (c)
12.75
- (d)
12.0
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