Practice Measurements And Instrumentation Multiple Choice Questions with Answers Quiz-4

Q.1.

In order to achieve accuracy, the slide wire of a potentiometer should be

as long as possible
as short as possible
neither too long nor too short
very thin

Q.2.

Assertion (A): CRO can be used to study waveshape accurately.

Reason (R): Input impedance of a CRO is very high.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.3.

Two wattmeter method for 3 phase power measurement can be used only for

balanced loads
unbalanced loads
both balanced and unbalanced loads
star connected loads

Q.4.

The advantage of LVDT over inductive bridge type transducer is that

it gives high output for small changes in core position
it can be used over a temperature range of - 265°C to 600°C
it can measure displacement of moving object
the error due to stray magnetic field is less

Q.5.

Acoustic strain gauges

have good linearity of measurement
do not have long term stability
have a large range of measurement
have an accuracy range of 0.1-1% depending on environment

Q.6.

A CT is used to feed current coils of wattmeter, energy meter, power factor meter and an ammeter. Then

all the coils are in series
all coils are in parallel
the coils are in series-parallel
either (a) or (b)

Q.7.

In measurements using strain gauge, the dummy strain gauge is used to

compensate for resistance of strain gauge
compensate for change in temperature
compensate for error due to change in voltage of battery
compensate for error in voltmeter

Q.8.

Which one of the following is true?

Alternating voltage and current contain odd and even harmonics
The inductance in a circuit reduces the effect of harmonics and makes current wave more sinusoidal than voltage wave
Alternating voltage and current waveforms, in general, do not contain odd harmonics
Inductance of a circuit does not alter wave shape at all

Q.9.

An oscilloscope has an input impedance consisting of 1 M&ohm; andpF is parallel. A high impedance probe connected to input of this oscilloscope has aM&ohm; series resistance. ThisM&ohm; series resistance

may not be shunted
should be shunted by 2 pF capacitor
should be shunted by 20 pF capacitor
should be shunted by 200 pF capacitor

Q.10.

Assertion (A): Damping in a vibration galvanometer is small.

Reason (R): Vibration galvanometer is a PMMC instrument.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.11.

Four capacitors are in parallel. Their values are 36.3 μF, 3.μF, 34.μF andμF with an uncertainty of digit in the last place. The total capacitance in significant figures is

75.0 μF
75.0 ± 0.1 μF
75.1 ± 0.1 μF
75.002 ± 0.1 μF

Q.12.

In measuring resistance using voltmeter and ammeter, the resistances of voltmeter and ammeter also affect the accuracy of measurement.

True
False

Q.13.

LVDT is used to measure

displacement
pressure
temperature
any of the above

Q.14.

The scale of PMMC instrument is linear.

True
False

Q.15.

A coil resonates at 1 MHz with a resonating capacitance ofpF. AtpF, resonance is obtained with a resonating capacitor ofpF. The self capacitance of coil is

12 pF
24 pF
30 pF
72 pF

Q.16.

In a Weston synchronoscope the deflecting torque is zero when

currents in fixed and moving coils are in phase
currents in fixed and moving coils are out of phase by 90°
currents in fixed and moving coils are out of phase by 60°
none of the above

Q.17.

In an ac single phase energy meter, the potential coil is put on

both side limbs, of upper magnet
central limb of upper magnet
one side limb of upper magnet
either (a) or (b)

Q.18.

The accuracy of a multimeter is about

± 3%
± 0.5%
± 0.01%
± 10%

Q.19.

Crompton potentiometer has

14 coils and a slide wire all having the same resistance
14 coils and a slide wire but the resistance of slide wire is half that of each coil
14 coils each of different resistance
14 coils out of which 7 coils have resistance which is twice that of remaining 7 coils

Q.20.

In a CRO the Y plates are oriented

horizontally
vertically
at an angle of 20° of horizontal
at an angle of 70° of horizontal

Q.21.

To measure moisture in wood, the most suitable method is

electric conduction
electrical-capacitive
absorption of radiation
equilibrium-moisture Vs humidity

Q.22.

A Weston frequency meter is

moving coil instrument
moving iron instrument
dynamometer instrument
induction instrument

Q.23.

Which of the following combinations is not used in thermocouple transducer measurement of temperature?

Iron-constantan
Chromel-aluminium
Copper-constantan
Iron-silver

Q.24.

The dynamic characteristics of capacitive transducer are similar to those of

LP filter
HP filter
notch filter
band stop filter

Q.25.

Which of the following is used as detector in audio frequency ac bridges?

AC voltmeter
CRO
Head phones
Vibration galvanometer

Q.26.

Assertion (A): The gall tinsley potentiometer is a coordinate potentiometer and has two exactly similar potentiometers.

Reason (R): An ac potentiometer may measure the unknown voltage in polar form or rectangular coordinate form.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.27.

Assertion (A): Thermistors are commonly used to measure hot spot temperatures in electric machines.

Reason (R): Thermistor has the advantages of high temperature coefficient, small size and high speed of response.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.28.

A peak responding ac voltmeter using a half wave rectifier has been calibrated to read 1 V for 1 V rms sine wave input. If input is 1 V dc the reading will be

0.707 V
0.707 or 0 V
1.414 V
1.414 or 0 V

Q.29.

Assertion (A): Megger is used to check insulation resistance of cables.

Reason (R): Insulation resistance of cables is very high.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.30.

The chemical effect of current is used in

dc ampere hour meter
dc ammeter
ac energy meter
all of the above

Q.31.

The output of a Piezoelectric crystal has

low amplitude and low impedance
high amplitude and low impedance
low amplitude and high impedance
high amplitude and high impedance

Q.32.

Induction wattmeter is an absolute instrument.

True
False

Q.33.

In a current transformers

the number of turns in primary and secondary windings are nearly equal
the number of primary turns is very small as compared to number of secondary turns.
the number of secondary turns is very small as compared to the number of primary turns
either (a) or (c).

Q.34.

Assertion (A): For best results the system of a D'Arsonval galvanometer should be slightly under damped.

Reason (R): Degree of damping affects the time taken by the instrument to come to final position.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.35.

The accuracy of an instrument is determined by

closeness of indicated value to the actual value
repeatability of measured value
speed with which the reading approaches final value
least value which can be measured

Q.36.

If σ standard deviation, probable error

σ
± 1.19 σ
± 0.6745 σ
± 0.4125 σ

Q.37.

An E transformer is a

displacement transducer
velocity transducer
acceleration transducer
pressure transducer

Q.38.

TheMHz in the specification of CRO means that

the sweep frequency is 10 MHz
the frequency of input signal should not be more than 10 MHz
the vertical amplifier has been designed for 10 MHz
none of the above

Q.39.

Rayleigh current balance is an absolute instrument.

True
False

Q.40.

The electrical power to a megger is provided by

battery
inverter
permanent magnet dc generator
ac generator

Q.41.

DC voltage of the order of a few mV can be accurately of measured by

PMMC voltmeters
moving iron voltmeter
null balancing potentiometer
electrostatic voltmeter

Q.42.

Absolute instruments are used in

laboratories
industries
power houses
standard laboratories

Q.43.

For measuring inductance with high Q, we should use

Maxwell's bridge
Maxwell Wien bridge
Hay's bridge
Either (a) or (b)

Q.44.

A resistance strain gauge has a resistance of about

100 &ohm;
25 &ohm;
10 &ohm;
1 &ohm;

Q.45.

Assertion (A): A power factor meter operates on dynamometer principle.

Reason (R): A power factor meter does not have a control spring.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true

Q.46.

The pressure coil of a wattmeter should be connected to the supply side of the current coil when

load impedance in high
load impedance is low
voltage is high
voltage is low

Q.47.

In a vibrating reed frequency meter the natural frequency of two adjacent reeds have a difference of

0.25 Hz
0.5 Hz
1.25 Hz
1 Hz

Q.48.

The time base of a high frequency CRO whose screen diameter iscm is set atμ sec/cm. The lowest frequency which can be fully displayed on the screen is

more than 100 kHz
equal to 100 kHz
equal to 10 kHz
less than 10 kHz

Q.49.

Eddy currents are essential for the deflecting torque of an induction wattmeter.

True
False

Q.50.

The torque in induction wattmeters due to

capacitive current
electrostatic effect
hall effect
eddy currents

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