ECE - Measurements and Instrumentation Quiz (or) MCQ

1 .

The scale of a dynamometer is linear when used as

A)

ammeter

B)

voltmeter

C)

wattmeter

D)

None of the above

Correct Answer : wattmeter

2 .

Thermistors are made of

A)

pure metals

B)

pure insulators

C)

pure semiconductors

D)

tintered mixture of metallic oxides

Correct Answer : tintered mixture of metallic oxides

3 .

Two sinusoidal signals of equal amplitude and frequency are applied to X and Y plate of CRO respectively. The observed Lissajous pattern is a straight line. The phase shift between signals is

A)

zero

B)

90°

C)

either zero or 180°

D)

either 90° or 270°

Correct Answer : either zero or 180°

4 .

Three phase four wire induction energy meter is used to measure

A)

energy in 3 phase unbalanced load

B)

energy in 3 phase balanced star load

C)

energy in 3 phase balanced delta load

D)

Either (B) or (C)

Correct Answer : energy in 3 phase unbalanced load

5 .

To measure a resistance of about 8 ohms we should use

A)

Meggar

B)

Wheatstone bridge

C)

Kelvin's double bridge

D)

Either (A) or (C)

Correct Answer : Wheatstone bridge

6 .

For measuring temperatures below 800Â°C with high accuracy, the best instrument is

A)

optical pyrometer

B)

thermistor based thermometer

C)

GaAs junction diode thermometer

D)

platinum resistance thermometer

Correct Answer : platinum resistance thermometer

7 .

Panel instruments are generally mounted vertically.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : True

8 .

Kelvin's double bridge is used to measure low resistances because

A)

it has high sensitivity

B)

there is no thermoelectric emf

C)

resistance variation due to temperature

D)

effect of contact and lead resistances is eliminated

Correct Answer : effect of contact and lead resistances is eliminated

Explanation : Effect of lead and contact resistances is very important in measurement of low resistances.

9 .

The resistance of a 125 Î© strain gauge changes by 1 ohm for 4000 micro strain. The gauge factor is

A)

1.5

B)

2

C)

2.5

D)

3

Correct Answer : 2

Explanation :

10 .

The D'Arsonval- movement can be converted into audio frequency ac ammeter by adding a

A)

rectifier

B)

chopper

C)

transducer

D)

thermocouple

Correct Answer : rectifier

Explanation : Rectifier converts ac to dc which is measured by D'Arsonval meter.

11 .

An accelerometer has a seismic mass of 0.05 kg and spring constant of 3 x 10⁵ N/m. If maximum displacement of mass is ± 1 mm, the maximum acceleration which can be measured is

A)

30 m/s²

B)

60 m/s²

C)

90 m/s²

D)

120 m/s²

Correct Answer : 60 m/s²

Explaination : 0.05 x a = 3 x 10³ x 10^-3 or a = 60 m/s².

12 .

A single element strain gauge bridge has two fixed resistances R₁ and R₁ of 120 Ω each and a variable resistance which gives full deflection at 120 Ω for zero strain and 120.6 Ω for straine e. If gauge factor is 2, strain e is

A)

0.0025

B)

0.0035

C)

0.005

D)

0.0075

Correct Answer : 0.0025

13 .

A moving iron voltmeter reads 250 V when connected to 250 V dc. If connected to 250 V 50 Hz, the voltmeter reading is likely to be

A)

210 V

B)

250 V

C)

248 V

D)

252 V

Correct Answer : 248 V

Explanation : The inductance of coil will allow slightly less ac current. Hence reading slightly less.

14 .

If an inductance L is connected in one arm of bridge and resistance R₁, R₂, R₃ in other three arms

A)

the bridge can be balanced

B)

the bridge cannot be balanced

C)

the bridge is balanced for some specific values of R₁, R₂, R₃

D)

the bridge is balanced for some specified value of frequency

Correct Answer :

the bridge cannot be balanced

Explaination : To balance the bridge both magnitudes and phase angles of voltages have to be balanced.

15 .

Which of the following method of measurement does a bridge circuit uses?

A)

absolute

B)

relative

C)

comparison

D)

differential

Correct Answer : comparison

Explanation : A bridge circuit makes use of a comparison measurement method. In this method the bridge compares the value of an unknown component with a standard value of a given component.

16 .

Which of the following is the most popular method for measuring low resistance?

A)

potentiometer method

B)

ducter ohmmeter method

C)

ammeter-voltmeter method

D)

kelvin double bridge method

Correct Answer : kelvin double bridge method

Explanation : Kelvin’s double bridge is used for the measurement of low resistances of the order of 1á¿¼ or less. Ammeter voltmeter method is used for the measurement of current flowing through and the voltage across the circuit.

17 .

Which of the following method is used for the measurement of Medium Resistance?

A)

Anderson Bridge

B)

Carey-Foster bridge method

C)

Direct-Deflection method

D)

Kelvinâ€™s double bridge method

Correct Answer : Carey-Foster bridge method

Explanation : Kelvin’s double bridge method is used for measurement of Low Resistance, Anderson Bridge is not used for measurement of Resistance, and Direct-Deflection method is used for Measurement of High Resistance.

18 .

Which of the following is the most sensitive detector for single frequency value?

A)

oscillator

B)

headphone

C)

tuned detector

D)

vibration galvanometer

Correct Answer : tuned detector

Explanation : A vibration galvanometer is used for detecting the balance condition. The oscillator is used as a source of the supply voltage. The tuned detector is the most sensitive detector for a single frequency value.

19 .

Under which of the following conditions a bridge is balanced?

A)

When no current flows

B)

When power dissipation is high

C)

When no voltage drop across the circuit

D)

When the temperature of the circuit is high

Correct Answer : When no current flows

Explanation : At balance condition, no current flows through the headphones present in the AC bridge circuit. As a result the detector indicates null deflection at balance condition.

20 .

To increase Q factor of a coil, the wire should be

A)

long

B)

thin

C)

thick

D)

long and thin

Correct Answer : thick

Explanation : Q is high if resistance is low. Therefore, wire should be thick.

21 .

An ammeter of 0-25 A range has a guaranteed accuracy of 1% of full scale reading. The current measured is 5 A. The limiting error is

A)

5%

B)

4%

C)

2.5%

D)

2%

Correct Answer : 5%

Explanation :

22 .

In a CRO which of the following is not a part of electron gun

A)

X - Y plates

B)

grid

C)

cathode

D)

accelerating anode

Correct Answer : X - Y plates

Explanation : Electron gun consists of cathode, grid and accelerating anode.

23 .

In 3 phase power measurement by two wattmeter method, the reading of one wattmeter is zero. The power factor of load is

A)

0

B)

0.5

C)

1

D)

0.8

Correct Answer : 0.5

Explanation : When p.f. = 0.5, 0 = 60° and one of the wattmeters reads zero.

24 .

The coil of a moving iron instrument has a resistance of 500 Ω and an inductance of 1 H. It reads 250 V when a 250 V dc is applied. If series resistance is 2000 Ω, its reading when fed by 250 V, 50 Hz ac will be

A)

260 V

B)

252 V

C)

250 V

D)

248 V

Correct Answer : 248 V

Explaination :

25 .

If reference sound pressure P₀ is 2 x 10^-5 N/m², a sound pressure of 90 dB is equal to

A)

0.632 N/m²

B)

0.707 N/m²

C)

0.835 N/m²

D)

0.925 N/m²

Correct Answer :

0.632 N/m²

Explaination :

26 .

Which of the following voltmeters would you use for measuring voltage across 20 kÎ© resistance?

A)

Voltmeter having a sensitivity of 1 kW/V

B)

Voltmeter having sensitivity of 10 kW/V

C)

Voltmeter having a resistance of 5 kÎ©

D)

None of the above

Correct Answer : Voltmeter having sensitivity of 10 kW/V

Explanation : Resistance of voltmeter should be very high as compared to 20 kΩ.

27 .

In which of the transformer is the secondary nearly short circuited under normal operating conditions?

A)

CT

B)

PT

C)

Power transformer

D)

Distribution transformer

Correct Answer : CT

Explanation : CT is operated with secondary short-circuited otherwise a high emf would be induced across secondary.

28 .

A single phase energy meter has the rating 1200 resolutions/ kWh. If a 500 W electric gadget is used for 4 hours, the energy meter will make

A)

1200 revolutions

B)

1800 revolutions

C)

2100 revolutions

D)

2400 revolutions

Correct Answer : 2400 revolutions

Explanation : 0.5 x 4 = 2 kWh = 2 x 1200 revolutions.

29 .

The current in a circuit is measured using a 150 : 1 CT If the ammeter reads 0.6 A, the circuit current is

A)

90 A

B)

144 A

C)

156 A

D)

250 A

Correct Answer : 90 A

Explanation : 150 x 0.6 = 90 A.

30 .

A Hall effect transducer has K_H = - 1 x 10^-8. If B = 1 Wb/m², I = 3 A and bismuth slab is 2 mm wide, the Hall voltage is

A)

-7.5 x 10^-6 V

B)

-15 x 10^-6

C)

-20 x 10^-4 V

D)

-22.5 x 10^-4 V

Correct Answer : -15 x 10^-6

Explaination :

31 .

Which of the following is not correct?

A)

A shunt should have a very low resistance

B)

Voltmeter should have a very high resistance

C)

An ammeter should have a very low resistance

D)

An electronic voltmeter draws appreciable current from source

Correct Answer : An electronic voltmeter draws appreciable current from source

Explaination : An electronic voltmeter draws negligible current.

32 .

Two ammeters A and B both 0-10 A have internal resistance of 1 Ω and 0.5 Ω respectively. They are connected in parallel. If total current is 15 A, then

A)

I_A = I_B = 7.5 A

B)

I_A = 10 A, I_B = 5 A

C)

I_A = 9 A, I_B = 6 A

D)

I_A = 5 A, I_B = 10 A

Correct Answer :

I_A = I_B = 7.5 A

33 .

The loss of charge method can be used to measure

A)

resistance of shunt

B)

resistance of shunt winding

C)

insulation resistance of cable

D)

None of the above

Correct Answer : insulation resistance of cable

Explanation : It is used for measuring very high resistance.

34 .

The resistance of a dc galvanometer is 20 Ω. A current of 10 mA causes full scale deflection. To convert it into 0-300 V voltmeter, we have to use a series resistance of

A)

15 Ω

B)

6000 Ω

C)

29980 Ω

D)

30000 Ω

Correct Answer : 29980 Ω

Explaination :

35 .

A capacitance transducer can be used to measure

A)

displacement

B)

level of fluids

C)

thickness of sheet

D)

All of the above

Correct Answer : All of the above

Explanation : In all these, change of capacitance occurs.

36 .

The dynamometer principle can be used for

A)

ammeter only

B)

voltmeter only

C)

wattmeter only

D)

ammeter, voltmeter and wattmeter

Correct Answer : ammeter, voltmeter and wattmeter

Explanation : Dynamometer principle can be used for ammeter, voltmeter and wattmeter. However it is generally used for wattmeters only.

37 .

The scale of hot wire ammeter is

A)

linear

B)

non-linear

C)

cramped

D)

absolute linear

Correct Answer : non-linear

Explanation : Since deflecting torque ∞ I², scale is non-linear.

38 .

A moving coil meter has a shunt of 0.02 Ω resistance. If coil resistance is 1000 Ω and a potential difference of 500 mV is required across it to cause full scale deflection, the current through shunt is

A)

25 A

B)

2.5 A

C)

0.25 A

D)

0.025 A

Correct Answer : 25 A

Explaination :

39 .

A 1 mA meter is to be converted to 1 A ammeter. The meter resistance is 100 Î©. The value of shunt resistance is

A)

0.001 Î©

B)

0.1001 Î©

C)

100 Î©

D)

1000 Î©

Correct Answer : 0.1001 Î©

40 .

The use of thermocouple meters for ac measurement leads to a scale which is

A)

linear

B)

square law

C)

logarithmic

D)

exponential

Correct Answer : square law

Explanation : Thermocouple meter is based on heating effect which varies as I².

41 .

Magnetic deflection is inversely proportional to

A)

voltage

B)

(voltage)0.5

C)

(voltage)1.5

D)

(voltage)2

Correct Answer : (voltage)0.5

Explanation :
where V_A is the potential difference between anode and cathode.

42 .

The most commonly used moving iron instruments are

A)

repulsion type

B)

attraction type

C)

a combination of attraction and repulsion type

D)

None of the above

Correct Answer : repulsion type

Explanation : Repulsion type have better accuracy.

43 .

In a thermocouple two metal junctions between metals M₁ and M₂ are kept at temperature T₁ and T₂. The thermocouple emf is produced because

A)

M₁, M₂ are similar and T₁, T₂ are equal

B)

M₁, M₂ are similar but T₁, T₂ are unequal

C)

M₁, M₂ are dissimilar but T₁, T₂ are unequal

D)

M₁, M₂ are dissimilar but T₁, T₂ are equal

Correct Answer :

M₁, M₂ are dissimilar but T₁, T₂ are unequal

Explaination : The two materials in thermocouple are different and the two junctions are kept at different temperatures.

44 .

A 300 V voltmeter has an accuracy of Â± 2% of full scale deflection. When the reading is 222 V, the actual voltage

A)

lies between 216 and 228 V

B)

is exact 222 V

C)

lies between 217.4 and 226.6 V

D)

lies between 217.56 and 226.44 V

Correct Answer : lies between 216 and 228 V

Explanation : Error = ± 6 V. Therefore, the actual value would be between 222 ± 6 V.

45 .

A moving iron instrument can be used for

A)

dc only

B)

ac only

C)

both dc and ac

D)

dc and high frequency ac

Correct Answer : both dc and ac

Explanation : Its deflecting torque ∝ I². So, it can be used for both d.c. and a.c.

46 .

Two voltmeters are each 0-300 V range. Their internal resistances are 10 kΩ and 20 kΩ They are connected is series and a voltage of 400 V is applied. Their readings respectively will be

A)

100 and 300 V

B)

200 V each

C)

266.6 and 133.3 V

D)

133.3 and 266.6 V

Correct Answer : 133.3 and 266.6 V

Explaination : The readings will be proportional to their internal resistance,

47 .

The resistance in the circuit of the moving coil of a dynamometer wattmeter should be

A)

high

B)

low

C)

very low

D)

almost zero

Correct Answer : high

Explanation : Moving coil is voltage coil and must have high resistance.

48 .

A temperature sensistive transducer is subjected to sudden temperature change. It takes 10 seconds for transducer to reach equilibrium condition (five times time constant). The time taken to reach half of temperature difference will be

A)

0.9 s

B)

1.38 s

C)

5 s

D)

8.62 s

Correct Answer : 1.38 s

Explaination : The initial change is fast.

49 .

One single phase wattmeter operating on 230V and 5A for 5 hours makes 1940 revolutions. Meter constant in revolutions is 400. What is the power factor of the land?

A)

0.65

B)

0.73

C)

0.84

D)

1

Correct Answer : 0.84

50 .

The spring material used in a spring control device should have the following property.

A)

Should be nonmagnetic

B)

Should have low specific resistance

C)

Most be of low temperature coefficient

D)

All of the above

Correct Answer : All of the above

51 .

Why is a MISC meter not recommended for DC measurement?

A)

The error is high due to hysteresis effect

B)

The meter does not respond to DC signals

C)

The error is high due to eddy current effect

D)

The meter is calibrated for AC and itâ€™s error for DC would be high

Correct Answer : The error is high due to hysteresis effect

52 .

A moving iron ammeter may be compensated for frequency errors by

A)

A series inductance

B)

Series resistance

C)

Shunt capacitance

D)

A shunt resistance

Correct Answer : Shunt capacitance

53 .

Which of the following meters has a linear scale?

A)

Hot wore meter

B)

Moving coil meter

C)

Moving iron meter

D)

Thermocouple meter

Correct Answer : Moving coil meter

54 .

A galvanometer has______

A)

Spring coil damping

B)

Eddy current damping

C)

Air friction damping

D)

Fluid friction damping

Correct Answer : Eddy current damping

55 .

A CRO can display

A)

AC signals

B)

DC signals

C)

Both AC and DC signals

D)

Time invariant signals

Correct Answer : Both AC and DC signals

56 .

A 10MHz CRO has________

A)

5MHz sweep

B)

10MHz vertical oscillator

C)

10MHz supply frequency

D)

10MHz horizontal oscillator

Correct Answer : 10MHz horizontal oscillator

57 .

When using ohmmeter, applied voltage is to be disconnected from the circuit because

A)

The ohmmeter has its own internal battery

B)

Current will decrease resistance

C)

Voltage source will increase resistance

D)

None of the above

Correct Answer : The ohmmeter has its own internal battery

58 .

For handling greater currents induction watt-meters are used in conjunction with

A)

Current transformers

B)

Power transformers

C)

Potential transformers

D)

None of the above

Correct Answer : Current transformers

59 .

Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured?

A)

Recording instruments

B)

Indicating instruments

C)

Absolute instruments

D)

Integrating instruments

Correct Answer : Indicating instruments

60 .

Which of the following are Integrating instruments?

A)

Wattmeters

B)

Ammeters

C)

Voltmeters

D)

Ampere-hour and Watt-hour meters

Correct Answer : Ampere-hour and Watt-hour meters

Explanation : Ampere-hour and Watt-hour meters are Integrating instruments.

61 .

Resistances can be measured with the help of

A)

Ammeters

B)

Voltmeters

C)

Wattmeters

D)

Ohmmeters and resistance bridges

Correct Answer : Ohmmeters and resistance bridges

Explanation : Resistances can be measured with the help of Ohmmeters and resistance bridges.

62 .

A _________ device prevents the oscillation of the moving system and enables the latter to reach its final position quickly

A)

Deflecting

B)

Damping

C)

Controlling

D)

Any of the above

Correct Answer : Damping

63 .

The torque in induction wattmeters due to

A)

eddy currents

B)

hall effect

C)

capacitive current

D)

electrostatic effect

Correct Answer : eddy currents

Explanation : Eddy currents are induced in the disc.

64 .

Two resistances are : R₁ = 36 Ω ± 1.89 Ω and R₂ = 75 Ω ± 3.75 Ω. The sum R₁ + R₂ along with limiting error is

A)

111 Ω ± 1.8 Ω

B)

111 Ω ± 1.95 Ω

C)

111 Ω ± 5.55 Ω

D)

111 Ω ± 3.75 Ω

Correct Answer : 111 Ω ± 5.55 Ω

Explaination :

36 + 75 = 111, 1.8 + 3.75 = 5.55.

Therefore, R₁ + R₂ = 111 ± 5.55 ohm.

65 .

An instrument of accuracy class 1 can have an error equal to

A)

+ 1% of reading

B)

Â± 1% of reading

C)

+ 1% of full scale deflection

D)

Â± 1% of full scale deflection

Correct Answer : Â± 1% of full scale deflection

66 .

Assertion (A): The scale a PMMC ammeter is linear.

Reason (R): The deflecting torque of PMMC is proportional to current in the coil.

A)

A is true R is false

B)

A is false R is true

C)

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

D)

Both A and R are true and R is correct explanation of A

Correct Answer : Both A and R are true and R is correct explanation of A

Explaination : Since the deflecting torque is proportional to current, the scale is linear.

67 .

A land line telemetry system is suitable for distance upto

A)

about 1 km only

B)

about 10 km only

C)

about 100 km only

D)

Any of the above

Correct Answer : about 1 km only

68 .

Use of high permeability core in moving iron instrument helps in

A)

reducing size of meter

B)

reducing temperature error

C)

increasing sensitivity

D)

All of the above

Correct Answer : increasing sensitivity

69 .

Shaft encoder is used to measure

A)

linear position

B)

angular position

C)

linear velocity

D)

linear acceleration

Correct Answer : angular position

70 .

The device having highest photo sensitivity is

A)

photodiode

B)

phototransistor

C)

photovoltaic cell

D)

photoconductive cell

Correct Answer : photoconductive cell

71 .

Which of the following closely represents the resistance-temperature characteristics of thermistor?

A)

R_T = a R₀ e^b/t

B)

R_T = a R₀ E^-b/t

C)

R_T = - R₀ e^b/t

D)

R_T = - a R₀ e^-b/t

Correct Answer : R_T = a R₀ e^b/t

72 .

LVDT is a________

A)

velocity transducer

B)

pressure transducer

C)

acceleration transducer

D)

displacement transducer

Correct Answer : displacement transducer

Explanation : It is used to measure displacement.

73 .

The dimensions of EMF are

A)

M^-1T^-3

B)

ML²I^-1T^-3

C)

ML²I^-2T^-3

D)

ML³I^-1T^-3

Correct Answer : ML²I^-1T^-3

74 .

A 0-200 V voltmeter has an accuracy of 0.75% of full scale reading. If voltage measured is 100 V, the error is

A)

.75%

B)

1.5%

C)

2%

D)

3%

Correct Answer : 1.5%

Explaination :

75 .

The power input and output in a device are 3650 W and 3385 W with each reading in doubt by ± 10 W. The percentage uncertainty in losses is

A)

± 15.09%

B)

± 11.32%

C)

± 7.55%

D)

± 3.77%

Correct Answer : ± 7.55%

Explaination : Losses = 3650 - 3385 = 265 W uncertainty = ± 20 W.

76 .

Two numbers are 131 Â± 5 and 629 Â± 3. The sum of the numbers with range of doubt is

A)

760 Â± 2

B)

760 - 8

C)

760 + 8

D)

760 Â± 8

Correct Answer : 760 Â± 8

Explanation : The numbers can be 131 + 5, 131 - 5, 629 - 3. Therefore, the sum can be 760 ± 8.

77 .

Which of these has a magnetic brake?

A)

Energy meter

B)

Frequency meter

C)

Thermocouple ammeter

D)

Dynamometer wattmeter

Correct Answer : Energy meter

Explanation : Braking torque, in an energy meter, is provided by a magnet.

78 .

A meter coil has a resistance of 100 Ω and a full scale deflection current of 10 mA. To convert it into a voltmeter of 0-200 V range, the series resistance should be

A)

1.9 kΩ

B)

19.9 kΩ

C)

20 kΩ

D)

20.1 kΩ

Correct Answer : 19.9 kΩ

Explaination :

79 .

Which of these has poor overload capacity?

A)

Hot wire instrument

B)

PMMC instrument

C)

Dynamometer instrument

D)

None of the above

Correct Answer : Hot wire instrument

Explanation : The wire is very delicate and has little over load capacity.

80 .

Which instrument is based on induction principle?

A)

Dynamometer wattmeter

B)

Induction wattmeter

C)

Energy meter

D)

Both (B) and (C)

Correct Answer : Both (B) and (C)

Explanation : Energy meter is also based on induction principle.

81 .

Unknown capacitance value is obtained by _________

A)

using a tuned detector

B)

comparison with standard

C)

using a vibration galvanometer

D)

using capacitance of other ratio arms

Correct Answer : comparison with standard

Explanation : Tuned circuit is used for detecting balance condition. Vibration galvanometer is used for the same purpose. Unknown value of capacitance is obtained by comparing it with a standard value.

82 .

Inductance control is obtained by _________

A)

using R₂

B)

using R₄

C)

using R₅

D)

using L_x

Correct Answer : using R₂

Explaination : In an inductance comparison bridge, the resistance R2 and R3 are variable. The value of resistance R2 is varied so as to control the inductance of the bridge.

83 .

A Schering bridge can be used for the _____________

A)

testing capacitors

B)

measuring voltages

C)

measuring currents

D)

protecting the circuit from temperature rises

Correct Answer : testing capacitors

Explanation : A Schering bridge can be used with both low voltage as well as high voltages. A Schering bridge is basically used for the measurement of small capacitances at low voltages with high precision.

84 .

What is the dependence of frequency on the balance equation?

A)

varies by a factor of 2

B)

independent

C)

depends on the detector used

D)

depends on the supply magnitude

Correct Answer : independent

Explanation : In a high voltage Schering bridge, the balance equation does not depend on the frequency of operation of the circuit. A detector is only used for detecting the balance condition in a bridge circuit.

85 .

Which of the following is the guarding arm?

A)

resistance R

B)

capacitance C

C)

parallel RC combination

D)

series RC combination

Correct Answer : parallel RC combination

Explanation : The series combination of R and C in a Wagner earth device forms a potential divider across the ratio arms. It is also known as the guard arm.

86 .

A moving coil instrument has a resistance of 0.6 Ω and full scale deflection at 0.1 A. To convert it into an ammeter of 0-15 A range, the resistance of shunt should be

A)

0.1 Ω

B)

0.6 Ω

C)

0.06 Ω

D)

0.004 Ω

Correct Answer : 0.004 Ω

87 .

A piezoelectric force transducer has a charge sensitivity of 20 pC/N. It is connected to a charge amplifier and overall gain of transducer and amplifier is 50 mV/N. The gain of amplifier is

A)

1 mV/pC

B)

1.5 mV/pC

C)

2.5 mV/pC

D)

4 mV/pC

Correct Answer : 2.5 mV/pC

88 .

An LVDT is used to measure displacement. The LVDT feeds a Voltmeter of 0-5 V range through a 250 gain amplifier. For a displacement 0.5 mm the output of LVDT is 2 mV. The sensitivity of instrument is

A)

1 V/mm

B)

5 V/mm

C)

0.1 V/mm

D)

0.5 V/mm

Correct Answer : 1 V/mm

Explaination : Final output = 2 x 10^-3 x 250 = 0.5 V.

89 .

In a ballistic galvanometer, a charge of 100 Î¼C gives a first swing of 25Â°. The charge required to cause first swing of 50Â° is

A)

25 Î¼C

B)

50 Î¼C

C)

200 Î¼C

D)

400 Î¼C

Correct Answer : 400 Î¼C

Explanation : swing is proportional to charge.

90 .

Two resistors R₁ = 36 Ω ± 5% and R₂ = 75 Ω ± 5% are connected in series. The total resistance is

A)

111 ± 0 Ω

B)

111 ± 5.55 Ω

C)

111 ± 2.778 Ω

D)

111 ± 7.23 Ω

Correct Answer :

111 ± 5.55 Ω

Explaination :
Total maximum error ± (1.8 + 3.75) = ± 5.55 Ω.

91 .

Which of the following can be measured using Maxwellâ€™s Inductance Capacitance Bridge?

A)

Inductance

B)

Frequency

C)

Capacitance

D)

Mutual Inductance

Correct Answer : Inductance

Explanation : For measuring Capacitance De-Sauty’s Bridge and Schering Bridge should be used. For measuring Frequency Wien’s Bridge is used. For measuring Mutual Inductance Heaviside and Campbell’s Bridge are used.

92 .

In a strain measuring device using a strain gauge, the output quantity is

A)

resistance

B)

voltage

C)

impedance

D)

None of the above

Correct Answer : voltage

Explanation : The measurement is done using an unbalanced bridge.

93 .

The angle Î´ for a mica capacitor is about

A)

1Â°

B)

5Â°

C)

15Â°

D)

25Â°

Correct Answer : 1Â°

Explanation : Mica capacitor has very low loss and loss angle δ is very very small.

94 .

A digital voltmeter has a read out range from 0 to 999 counts. If the full scale reading is 9.999 V, the resolution is

A)

0.01 V

B)

1 V

C)

1 mV

D)

1 Î¼V

Correct Answer : 1 mV

Explanation : Resolution is the smallest change in the quantity being measured which will cause an observable change in output. In this case it is 1 mV.

95 .

The coil of a moving coil meter has 100 turns, is 40 mm long and 30 mm wide. The control torque is 240 x 10^-6 N-m on full scale. If B = 1 Wb/m², range of meter is

A)

1 mA

B)

2 mA

C)

3 mA

D)

4 mA

Correct Answer : 2 mA

Explaination :

96 .

Which one of the following effects is used in measuring power?

A)

Hall

B)

Ferrari

C)

Seeback

D)

Induction

Correct Answer : Induction

Explanation : Induction wattmeter.

97 .

The effect of lead resistance is important in measurement of

A)

resistance of shunt

B)

resistance of ammeter

C)

resistance of shunt winding

D)

Both (A) and (B)

Correct Answer : Both (A) and (B)

Explanation : Lead resistance is important when measuring low resistance. Resistance of shunt and ammeter is low.

98 .

A resistance wire strain gauge has gauge factor 2. If stress is 100 mega newton/m² and Young's modulus is 200 giga newton/ m², the percentage change in gauge resistance due to stress is

A)

0.1

B)

0.2

C)

0.4

D)

0.5

Correct Answer : 0.1

Explaination :

99 .

Insertion of a dielectric material between the plates of an air capacitor

A)

decreases capacitance

B)

increases the capacitance

C)

has no effect an capacitance

D)

increases breakdown voltage

Correct Answer : increases the capacitance

100 .

Two ammeters A and B are connected in parallel in a circuit carrying 100 A. Their resistances are 0.8 mÎ©. Their readings will be.

A)

40 A and 60 A respectively

B)

44.44 A and 55.56 A respectively

C)

55.56 and 44.44 A respectively

D)

60 A and 40 A respectively

Correct Answer : 55.56 and 44.44 A respectively

Explanation :

101 .

In household energy meters the flux of series magnet is in phase with current but the flux of shunt magnet lags the voltage by 88°. The reading of energy meters

A)

will be correct

B)

will have a negative error

C)

will have a positive error

D)

may have positive or negative error

Correct Answer : will have a negative error

Explaination : Since angle is less than 90°, reading will be less. Therefore error is negative and correction is positive.

102 .

The power factor of a single phase load can be calculated if instruments available are

A)

two ammeters

B)

two voltmeters

C)

one voltmeter, one ammeter

D)

one voltmeter, one ammeter and one wattmeter

Correct Answer : one voltmeter, one ammeter and one wattmeter

Explanation :
we need to, measure active power, voltage and current.

103 .

The current through the coil of an electromagnet is doubled. The magnetic field around the coil

A)

is doubled

B)

is halved

C)

remains the same

D)

becomes four times

Correct Answer : is doubled

Explanation : B ∝ H.

104 .

A variable reluctance type tachometer has 150 teeth on rotor. The counter records 13500 pulse/sec. The rotational speed is

A)

4800 RPM

B)

5400 RPM

C)

6000 RPM

D)

7200 RPM

Correct Answer : 5400 RPM

Explanation :

105 .

In a moving iron voltmeter the coil has a resistance of 20 Ω and an inductance of 0.3 H. The swamping resistance in 2000 Ω. To ensure correct reading with dc as well as 50 Hz ac, the value of capacitor to be connected in parallel with swamping resistance should be

A)

0.0125 μF

B)

0.0311 μF

C)

0.0521 μF

D)

0.0622 μF

Correct Answer : 0.0311 μF

Explaination :

C = 0.41 L/R²

or C = (0.41 x 0.3)/(2000)² = 0.0311 x 10^-6 F.

106 .

The current passing through a resistance of 100 ± 0.2% Ω is 2 ± 0.5% A. The limiting error in computation of power will be

A)

± 0.3%

B)

± 0.7%

C)

± 0.9%

D)

± 1.2%

Correct Answer : ± 1.2%

Explaination : Limiting error = 2 x 0.5 + 0.2 = ± 1.2% (we have to take 2 x 0.5 because power ∝ I²).

107 .

If the secondary burden of a CT 15 VA and secondary current is 5 A, the load impedance of CT is

A)

0.6 Î©

B)

5 Î©

C)

6 Î©

D)

10 Î©

Correct Answer : 0.6 Î©

Explanation :

108 .

In a CRO, the frequency of output of time base generator

A)

is adjustable

B)

varies automatically

C)

is only one constant value

D)

Either (B) or (C)

Correct Answer : is adjustable

Explanation : Time base signal frequency is adjustable so that voltages of different frequencies can be measured.

109 .

A 0-150 voltmeter has a guaranteed accuracy of 1% of full scale reading. If actual reading is 83 V, the percentage error is

A)

0.83%

B)

1%

C)

1.81%

D)

None of the above

Correct Answer : 1.81%

Explanation :

110 .

If A = 131 Â± 4 and B = 106 Â± 4, the percentage range of doubt in A - B is

A)

4%

B)

8%

C)

16%

D)

32%

Correct Answer : 32%

Explanation : (A - B) = 25 ± 8. Therefore, % range of doubt = 8/25 x 100 =32%

111 .

Two resistance R₁ and R₂ are connected in series R₁ = 528 ± 5 Ω and R₂ = 325 ± 3Ω. The total resistance will be

A)

853 ± 2 Ω

B)

853 ± 3 Ω

C)

853 ± 5 Ω

D)

853 ± 8 Ω

Correct Answer : 853 ± 8 Ω

Explaination :

Both errors can be positive or negative simultaneously.

Hence 853 ± 8 Ω.

112 .

It is necessary to measure the amplitudes of two signals and also the phase difference between them. This can be done by using a

A)

phase meter

B)

waveform meter

C)

digital voltmeter

D)

vector voltmeter

Correct Answer : waveform meter

Explanation : A waveform meter is suitable to study amplitudes, phase angles etc. of different waveforms.

113 .

Which of the following does not use the principle of change in inductance?

A)

LVDT

B)

Reluctance pick up

C)

Strain gauge

D)

Inductance displacement transducer

Correct Answer : Strain gauge

Explanation : In strain gauge change in resistance occurs.

114 .

The function of shunt in an ammeter is to

A)

by pass the current

B)

increase sensitivity of meter

C)

increase resistance of meter

D)

All of the above

Correct Answer : by pass the current

Explanation : It bypasses a major portion of circuit current so that only the rated current of meter can flow through the meter.

115 .

Four voltmeters have following specifications. If accuracy is main consideration which is the best?

A)

100 V, 100 mA

B)

100 V, 2 mA

C)

100 V, 1 mA

D)

100 V, 0.1 mA

Correct Answer : 100 V, 0.1 mA

Explanation : Since the current drawn is minimum, the accuracy is maximum.

116 .

A wire strain gauge has a gauge factor of 2, resistance of 125 Ω and length 1 m. If length of wire changes by .005 m, change in resistance will be

A)

0.25 Ω

B)

0.5 Ω

C)

1.25 Ω

D)

2.5 Ω

Correct Answer : 1.25 Ω

Explaination :

117 .

To avoid creep in an energy meter

A)

the potential coil is made of very thin wire

B)

two shading bands are put on series magnet

C)

two shading bands are put on shunt magnet

D)

two holes are cut in the disc on opposite sides of spindle

Correct Answer : two holes are cut in the disc on opposite sides of spindle

Explanation : When a hole comes under a pole of upper electromagnet the disc becomes stationary. Thus creep is avoided.

118 .

A sinusoidal signal is measured by CRO. The scale is set at 4 mV/cm. If vertical distance between positive and negative peaks is 6 cm, the peak value of ac signal is

A)

3 mV

B)

6 mV

C)

12 mV

D)

24 mV

Correct Answer : 12 mV

Explaination :
Peak to peak value will be 24 mV.

119 .

The deflection of a DArsonval galvanometer is measured through a mirror and scale. The mirror is 1 m away from the light source. The mirror is mounted on, the moving system. If mirror rotates through 0.2 rad the displacement on the scale is

A)

0.05 m

B)

0.1 m

C)

0.2 m

D)

0.4 m

Correct Answer : 0.4 m

Explaination : Diplacement = (1) (2θ) = 0.4 m.

120 .

Two ammeters having resistances of 0.5 Ω and 0.25 Ω and having full scale reading of 25 A each are connected in parallel. To ensure that neither of them goes beyond scale, the total current should not be more than

A)

25 A

B)

37.5 A

C)

40 A

D)

50 A

Correct Answer :

37.5 A

Explaination :

121 .

The dead zone in a pyrometer is 0.125% of span. The calibration is 400Â°C to 1000Â°C. What temperature change might occur before it is detected.

A)

0.125Â°C

B)

0.4Â°C

C)

0.75Â°C

D)

1Â°C

Correct Answer : 0.75Â°C

Explanation :

122 .

A polyphase wattmeter basically consists of two wattmeters. The moving system of two wattmeters

A)

are common

B)

are separate

C)

are generally separate

D)

are generally common

Correct Answer : are common

Explanation : The moving system has to be common since reading depends on the action of both wattmeters.

123 .

A megger is usually

A)

Hot-wire type instrument

B)

Moving coil type instrument

C)

Moving iron type instrument

D)

Electro-static type instrument

Correct Answer : Moving coil type instrument

124 .

Ampere is one of the

A)

Base units

B)

Derived units

C)

Supplementary units

D)

Units used to measure charge

Correct Answer : Base units

125 .

The internal resistance of an ammeter should be

A)

High

B)

Medium

C)

Infinity

D)

Very small

Correct Answer : Very small

126 .

A rectifier type instrument is connected to 100VDC and is operated in the DC measuring module reads

A)

50V

B)

90V

C)

100V

D)

111V

Correct Answer : 111V

127 .

An oscilloscope indicates

A)

RMS value

B)

Average value

C)

Peak to peak value of voltage

D)

DC value of voltage

Correct Answer : Peak to peak value of voltage

128 .

Ryall crest voltmeter is used for measurement of

A)

High DC voltage

B)

High AC voltage

C)

AC voltage of any form

D)

Low frequency voltage

Correct Answer : High AC voltage

129 .

Direct method is used to measure

A)

Length

B)

Voltage

C)

Pressure

D)

Temperature

Correct Answer : Length

130 .

The resistance can be measured most accurately by

A)

Megger

B)

Bridge method

C)

Multimeter

D)

Voltmeter-ammeter method

Correct Answer : Bridge method

131 .

In a ballistic galvanometer, the deflecting torque is proportional to

A)

Sine of measured

B)

The current through coil

C)

Square of current through coil

D)

Square-root of current through coil

Correct Answer : The current through coil

132 .

In a moving coil instrument, the deflecting torque is proportional to

A)

Current

B)

Square of the current

C)

Sine of the measurand

D)

Squareroot of the current

Correct Answer : Current

133 .

In a moving iron meter, the deflecting torque is proportional to

A)

Sine of the measurand

B)

Current through the coil

C)

Squareroot of the measurand

D)

Square of the current through the coil

Correct Answer : Square of the current through the coil

134 .

Which wave has the least form factor?

A)

Sine wave

B)

Triangular wave

C)

Square wave

D)

Rectangular wave

Correct Answer : Square wave

135 .

The current coil of a wattmeter is connected to the CT of R-phase. The potential coil is connected across Y and B phases. The wattmeter measures

A)

Active power of Y phase

B)

Active power in R phase

C)

Reactive power of R phase

D)

Power proportional to 3 phase power if the load is balanced

Correct Answer : Reactive power of R phase

136 .

Two voltmeters have the same range 0-400V. The internal impedance are 30,000 Ohms and 20,000 Ohms. If they are connected in series and 600V be applied across them, the readings are

A)

300V each

B)

360V and 240V

C)

400V and 200V

D)

One of the meters out of the range and other 100V

Correct Answer : 360V and 240V

137 .

The two pressure coils of a single phase power factor meter have

A)

The same dimension but different number of turns

B)

The same dimensions and the same number of turns

C)

The same number of turns but different dimensions

D)

None of the above

Correct Answer : The same dimensions and the same number of turns

138 .

To measure the flux, devices used are based on

A)

Hall effect

B)

Voltaic effect

C)

Piezo-electric effect

D)

Photo-voltaic effect

Correct Answer : Hall effect

139 .

No eddy current and hysteresis losses occur in

A)

PMMC instruments

B)

Electrostatic instruments

C)

Moving iron instruments

D)

Electrodynamo meter instruments

Correct Answer : Electrostatic instruments

140 .

The absolute measurement of resistance is done by

A)

Bridge Method

B)

Rayleigh method

C)

Ohmâ€™s law method

D)

Lorenz method

Correct Answer : Lorenz method

141 .

For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging

A)

One of the wattmeters will read zero

B)

Both give the same readings

C)

Pressure coil of the wattmeter will become ineffective

D)

One of the wattmeter connections will have to be reversed

Correct Answer : One of the wattmeter connections will have to be reversed

142 .

For use at 50 Hz the range of scale of vibrating reed frequency meter is

A)

25 - 75 Hz

B)

40 - 60 Hz

C)

47 - 53 Hz

D)

42 - 58 Hz

Correct Answer : 47 - 53 Hz

Explanation : Generally the frequency does not fall below 47 Hz and does not exceed 53 Hz.

143 .

The two pressure coils in a single phase power factor meter of turns

A)

the same dimension and the same numbers of turns

B)

the same dimension but different number of turns

C)

different dimension and different numbers of turns

D)

different dimension but the same numbers of turns

Correct Answer : the same dimension and the same numbers of turns

144 .

Piezoelectric effect can be used to measure

A)

force

B)

strain

C)

acceleration

D)

All of the above

Correct Answer : All of the above

145 .

A current of 3.18 A is flowing through resistance of 35.68 Ω. The voltage drop across resistance to the appropriate number of significant figures is

A)

113 V

B)

113.46 V

C)

113.462 V

D)

113.4624 V

Correct Answer : 113 V

146 .

A current of 3.25 A is flowing through a resistance of 34.98 Ω. The voltage drop across resistance to the appropriate number of significant figures is

A)

113.6 V

B)

113.68 V

C)

113.685 V

D)

114 V

Correct Answer : 114 V

147 .

In dc tacho generators used for measurement of speed of shaft, frequent calibration is necessary because

A)

there is back emf

B)

contacts wear off

C)

strength of permanent magnet decreases with age

D)

armature current produces heating effect

Correct Answer : strength of permanent magnet decreases with age

148 .

To measure a resistance by a dc potentiometer

A)

it is necessary to use a volt ratio box

B)

it is not necessary to standardise the potentiometer

C)

it is necessary to standardise the potentiometer

D)

None of the above

Correct Answer : it is not necessary to standardise the potentiometer

149 .

A voltage of about 200 V dc can be measured

A)

directly by dc potentiometer

B)

by dc potentiometer in conjunction with a volt ratio box

C)

a dc potentiometer in conjunction with a known resistance

D)

None of the above

Correct Answer : by dc potentiometer in conjunction with a volt ratio box

150 .

De Sauty bridge is very widely used due to

A)

simplicity

B)

maximum sensitivity

C)

perfect balance for imperfect capacitor

D)

perfect balance for air capacitors

Correct Answer : simplicity

151 .

A Weston synchronoscope is a

A)

induction instrument

B)

moving iron instrument

C)

moving coils instrument

D)

dynamometer instrument

Correct Answer : dynamometer instrument

152 .

In a dynamometer 3 phase power factor meter, the planes of the two moving coils are at

A)

0Â°

B)

60Â°

C)

90Â°

D)

120Â°

Correct Answer : 120Â°

153 .

A generated voltage is equally dependent on three resistances R₁, R₂, R₃ and its value is V = (R₁R₂)/R₃. If tolerance of each resistor is 0.1%, the maximum error in voltage is

A)

± 0.1%

B)

± 0.3%

C)

0.1%

D)

0.3%

Correct Answer :

± 0.3%

Explaination : The tolerances are additive.

154 .

In an Anderson bridge the unknown inductance is measured in terms of

A)

known capacitance

B)

known inductance

C)

known capacitance and resistance

D)

known inductance and resistance

Correct Answer : known capacitance and resistance

155 .

In a Ballistic galvanometer

A)

inertia is large and damping is small

B)

both inertia and damping are large

C)

inertia is large and damping is critical

D)

inertia is small and damping is also small

Correct Answer : inertia is large and damping is small

156 .

Which instrument needs creep compensation?

A)

Energy meter

B)

Induction wattmeter

C)

Dynamometer wattmeter

D)

None of the above

Correct Answer : Energy meter

157 .

When deflecting torque and braking torque in an energy meter are zero,

A)

the disc retards

B)

the disc accelerates

C)

the disc is stationary

D)

the disc rotates at steady speed

Correct Answer : the disc rotates at steady speed

158 .

For measuring mutual inductance we can use

A)

Maxwell's bridge

B)

Anderson bridge

C)

Heaviside bridge

D)

None of the above

Correct Answer : Heaviside bridge

159 .

A dual trace CRO has_____

A)

one electron gun

B)

two electron guns

C)

one electron gun with one two pole switch

D)

two electron guns with one two pole switch

Correct Answer : one electron gun with one two pole switch

160 .

The sensitivity of a voltmeter using 0-5 mA meter movement is

A)

500 Î©/V

B)

200 Î©/V

C)

100 Î©/V

D)

50 Î©/V

Correct Answer : 200 Î©/V

161 .

Two meters X and Y require 40 mA and 50 mA for full scale deflection. Then

A)

X is more sensitive

B)

Y is more sensitive

C)

both are equally sensitive

D)

it is not possible to determine from given data

Correct Answer : it is not possible to determine from given data

162 .

The volt ratio box is basically a

A)

potential divider

B)

current transformer

C)

a high resistance voltmeter

D)

None of the above

Correct Answer : potential divider

Explanation : DC potentiometer can measure voltages upto about 1.5 V. Volt ratio box is used to reduce the unknown voltage so that it can be measured by dc potentiometer.

163 .

A sinusoidal ac voltage of amplitude 100 V is applied to a rectifying device which offers 10 Ω resistance in forward direction and infinite resistance in backward direction. A moving coil ammeter is also connected in the circuit. The reading of ammeter will be

A)

3.185 A

B)

5 A

C)

10 A

D)

14.14 A

Correct Answer : 3.185 A

Explaination : Moving coil instrument indicates average value

164 .

A variable reluctance tachometer has 180 teeth on rotor. The speed of shaft on which it is mounted in 1200 rpm. The frequency of output pulses is

A)

1800 per second

B)

3600 per second

C)

4800 per second

D)

5600 per second

Correct Answer : 3600 per second

Explaination :

165 .

Two voltmeters 0-250 V each having resistances of 5 kΩ and 10 kΩ respectively and are connected in series. To ensure that neither of them goes beyond scale the total voltage which can be applied should be less than

A)

500 V

B)

400 V

C)

375 V

D)

250 V

Correct Answer :

375 V

Explaination :

166 .

A 24 mm long conductor has a resistance of 128 Ω. The change in resistance is 13.3 Ω and change in length is 1.6 mm under tension. The gauge factor is

A)

1.2

B)

1.6

C)

2.1

D)

2.6

Correct Answer : 1.6

Explaination :

167 .

In a digital measuring device the input electrical signal is in the frequency range of dc to ac (50) Hz. It must be sampled at a rate of

A)

2 f times/sec

B)

0.5 f times/sec

C)

0.25 f times/sec

D)

f times/sec

Correct Answer : 2 f times/sec

Explaination : Sampling frequency must be twice the input frequency.

168 .

Measuring of unknown voltage with a dc potentiometer loses its advantage of open circuit measurement when

A)

primary circuit battery is changed

B)

voltage is larger than range of potentiometer

C)

standardisation is done to compensate for drift

D)

range reduction by factor of 10 is employed

Correct Answer : range reduction by factor of 10 is employed

Explanation : When volt ratio box is used to reduce range, the advantage of open-circuit measurement is lost.

169 .

PCM employing 4 bit code is used to send data having frequency range from 0 to 2 kHz. The minimum required bandwidth of carrier channel is

A)

2 kHz

B)

4 kHz

C)

8 kHz

D)

16 kHz

Correct Answer : 4 kHz

Explaination : Bandwidth required is twice the required frequency range.

170 .

A sinusoidal ac voltage of amplitude 100 V is applied to a rectifying device which offers 10 Ω resistance in forward direction and infinite resistance in reverse direction. The reading on hot wire ammeter will be

A)

1.414 A

B)

3.185 A

C)

5 A

D)

10 A

Correct Answer : 5 A

Explaination : Hot wire ammeter indicates rms value

171 .

When a capacitor is connected to the terminals of an ohmmeter, the pointer indicated a low resistance initially and finally come to infinity position. This shows that capacitor is

A)

short circuited

B)

faulty

C)

all right

D)

open circuited

Correct Answer : all right

Explaination : Capacitor behaves as short circut initially and open circuit finally when fed by dc supply.

172 .

If eddy current damping is to be used, the disc of instrument should be

A)

conducting and magnetic

B)

conducting and non-magnetic

C)

non-conducting and magnetic

D)

non-conducting and non-magnetic

Correct Answer : conducting and non-magnetic

Explanation : Disc must be conducting otherwise eddy currents can not flow. It must be non-magnet, i.e., so that it does not affect the measurement.

173 .

With a variable reluctance tachometer having 60 rotor teeth the count reads 3600 counts per minute. The speed in RPM is

A)

36

B)

60

C)

360

D)

3600

Correct Answer : 60

Explanation : If speed is 60, the counter will count 60 x 60 = 3600 counts/per minute.

174 .

It is required that a strain gauge has gauge factor of 100. The proper strain gauge is

A)

nichrome strain gauge

B)

alloy strain gauge

C)

semiconductor strain gauge

D)

constantan strain gauge

Correct Answer : semiconductor strain gauge

Explanation : Only semiconductor strain gauge can have a gauge factor of 100. For all other strain gauges, gauge factor is about 2 only.

175 .

A meter having 0-1000 μA range and 1000 Ω resistance is required to be changed to 0-100 mA meter. The value of shunt resistance is about

A)

1 Ω

B)

10 Ω

C)

99 Ω

D)

100 Ω

Correct Answer : 10 Ω

Explaination :

176 .

An induction wattmeter can be used for

A)

dc only

B)

50 Hz ac only

C)

both ac and dc

D)

high frequency ac only

Correct Answer : 50 Hz ac only

Explanation : Induction principle is valid for ac only. Induction Instruments are calibrated for 50 Hz ac.

177 .

If the current in a capacitor leads the voltage by 80Â°, the loss angle of capacitor is

A)

10Â°

B)

80Â°

C)

100Â°

D)

170Â°

Correct Answer : 10Â°

Explanation : Loss angle δ = 90 - 80 = 10°.

178 .

A multiplier is __________

A)

capacitive

B)

resistive

C)

non-inductive

D)

non-capacitive

Correct Answer : non-inductive

Explanation : A multiplier is basically a non-inductive, high resistance that is used to extend the range of a D.C. voltmeter. Multiplier consists of a low range D.C. voltmeter connected in series with it.

179 .

The windings of a C.T. are ________

A)

shorted

B)

grounded

C)

tied together

D)

wound over one another

Correct Answer : wound over one another

Explanation : Using cylinders made of Bakelite, the windings of a C.T. are wound over one another. This setup is mounted on a steel tank sheet filled with transformer oil.

180 .

How is the voltage ratio dependent on the frequency?

A)

they oppose each other

B)

they aid each other

C)

depends on the setup of the circuit

D)

they are independent of each other

Correct Answer : they oppose each other

Explanation : As the voltage ratio changes, the frequency also changes. It depends on the relative value of the core loss component Io as well as the leakage reactance. The effects due to the voltage ratio and the change in frequency oppose each other.

181 .

A meter with a resistance of 100 Ω and a full scale deflection of current of 1 mA is to be converted into voltmeter of 0 - 5 V range. The multiplier resistance should be

A)

490 Ω

B)

4900 Ω

C)

5000 Ω

D)

5100 Ω

Correct Answer : 4900 Ω

Explaination :

182 .

The household energy meter is

A)

recording instrument

B)

indicating instrument

C)

integrating instrument

D)

None of the above

Correct Answer : integrating instrument

Explanation : It integrates energy over a period of time.

183 .

A standard cell of 1.0185 V is used with a slide wire potentiometer. The balance was obtained at 60 cm. When an unknown emf was connected, the balance was obtained at 82 cm. The magnitude of unknown emf is

A)

1.39 V

B)

7.45 V

C)

13.9 V

D)

15.0 V

Correct Answer : 1.39 V

Explaination :

184 .

In a resistance strain gauge, G = 2, stress = 1050 kg/cm², R = 1000 Ω. The value of ΔR will be

A)

1 Ω

B)

2 Ω

C)

3 Ω

D)

4 Ω

Correct Answer : 1 Ω

Explaination :

185 .

A moving coil instrument has a resistance of 0.5 Î© and a full scale deflection of 0.1 A. To convert it into an ammeter of 0-10 A the shunt resistance should be

A)

0.006 Î©

B)

0.005 Î©

C)

0.05 Î©

D)

0.1 Î©

Correct Answer : 0.005 Î©

186 .

Potentiometer method of dc voltage measurement is more accurate than direct measurement using a voltmeter because

A)

it loads the circuit moderately

B)

it loads the circuit to maximum extent

C)

it does not load the circuit at all

D)

it uses centre zero galvanometer instead of Voltmeters

Correct Answer : it does not load the circuit at all

Explanation : Since the circuit is not loaded, the accurate value of dc voltage is measured.

187 .

Which of the following is true about an impulse voltage?

A)

It is a unidirectional voltage

B)

Chopped impulse flashover does not occur

C)

Time taken to rise is equal to time taken to fall

D)

RMS value is always less than 50% of average value

Correct Answer : It is a unidirectional voltage

Explanation : Impulse is unidirectional (either positive or negative).

188 .

Which of the following are needed both for protection and metering?

A)

Wattmeters

B)

Energy meters

C)

Power factor meters

D)

Instrument transformers

Correct Answer : Instrument transformers

Explanation : Instrument transformers are used to measure high currents and voltages. They also feed the relays for protection.

189 .

A voltmeter using thermocouples measures

A)

rms value

B)

peak value

C)

average value

D)

peak to peak value

Correct Answer : rms value

Explanation : Since the thermocouple is based on heating effect, rms value is measured.

190 .

The speed transducer using a drag cup rotor has the main advantage of

A)

cheap construction

B)

very high accuracy

C)

low energy requirement

D)

All of the above

Correct Answer : low energy requirement

Explanation : A drag cup rotor has low inertia. Therefore it requires little amount of energy.

191 .

A digital frequency counter can be converted to DVM by addition of a suitable

A)

D/A converter

B)

power amplifier

C)

operational amplifier

D)

voltage controlled oscillator

Correct Answer : D/A converter

Explanation : D/A converter changes digital output to analog output.

192 .

A dynamometer wattmeter is connected in ac circuit. The reading will be

A)

peak power

B)

V-A product

C)

average power

D)

instantaneous power

Correct Answer : average power

Explanation : Wattmeter measures average power over a cycle.

193 .

The input impedance of CRO is about

A)

zero

B)

10 Î©

C)

100 Î©

D)

one mega ohm

Correct Answer : one mega ohm

Explanation : CRO has very high input impedance.

194 .

The response of a thermistor overs the whole of its temperatures range is

A)

linear

B)

non-linear

C)

almost linear

D)

Either (A) or (C)

Correct Answer : non-linear

Explanation : It is a non-linear device. The change of resistance with temperature is non-linear.

195 .

Which of the following is not correct in respect of electrostatic instrument?

A)

It has a uniform scale

B)

It is essentially a voltmeter

C)

It can be used for both ac and dc

D)

It is suitable for only high voltages

Correct Answer : It has a uniform scale

Explanation : The scale of electrostatic voltmeter is not uniform.

196 .

The wave applied to X plates, for ohtaining trace of voltage wave, is

A)

sinusoidal wave

B)

sawtooth wave

C)

rectangular wave

D)

None of the above

Correct Answer : sawtooth wave

Explanation : It is called time base signal.

197 .

It is required to study transients during switching process. Which CRO should be preferred?

A)

Ordinary CRO

B)

Dual trace CRO

C)

Dual beam CRO

D)

Storage oscilloscope

Correct Answer : Storage oscilloscope

Explanation : We can store the trace.

198 .

The percentage limiting error in an instrument reading 8.3 V and having guaranteed accuracy of 1% of the full scale reading and range of 0-150 V is

A)

0.0018%

B)

0.181%

C)

1.81%

D)

18.1%

Correct Answer : 18.1%

Explaination :

199 .

If the secondary winding of CT is opened when primary coil is carrying current

A)

transformer will burn immediately

B)

there will be weak flux density in core

C)

there will be high current in secondary

D)

there will be very high induced voltage in secondary

Correct Answer : there will be very high induced voltage in secondary

Explanation : Since the primary of CT always remains excited, a high voltage is induced in secondary if the secondary is opened.

200 .

A meter has a resistance of 1 Î© and full scale deflection current of 1 mA. To convert into an ammeter of 1 A range, the shunt resistance should be

A)

0.001 Î©

B)

0.01 Î©

C)

1 Î©

D)

1000 Î©

Correct Answer : 0.001 Î©

Explanation :

201 .

A radiation thermometer is suitable for temperatures

A)

below 100Â°C

B)

below 500Â°C

C)

above 500Â°C

D)

above 1400Â°C

Correct Answer : above 1400Â°C

Explanation : It is suitable for only very high temperatures.

202 .

A rectifier voltmeter using bridge rectifier and PMMC meter is calibrated to read rms value of sine wave. A triangular wave is applied to it and it reads 6.82 V. The rms value of triangular wave is

A)

about 6.5 V

B)

about 6.82 V

C)

about 7.1 V

D)

about 10 V

Correct Answer : about 7.1 V

Explaination :

203 .

A moving coil meter has 10 Ω resistance and requires 40 mA for full scale deflection. The shunt resistance required to convert it into 0-2 A ammeter is

A)

0.1021 Ω

B)

0.2041 Ω

C)

0.256 Ω

D)

0.4210 Ω

Correct Answer : 0.2041 Ω

Explaination :

204 .

An amplifier has to amplify pulses of 1 H-s duration. The minimum bandwidth of amplifier must be

A)

1 kHz

B)

1 MHz

C)

10 kHz

D)

10 MHz

Correct Answer : 1 MHz

Explanation : Time period of 1 μs corresponds to frequency of 1 MHz.

205 .

A moving coil meter has a resistance of 50 ohms and a full scale deflection current of 20 mA. To convert it into a voltmeter of 0-100 V range, the series resistance should be

A)

4950 Ω

B)

5000 Ω

C)

5050 Ω

D)

5500 Ω

Correct Answer : 4950 Ω

Explaination :

206 .

In measuring a resistance by voltmeter-ammeter method, the voltmeter can be connected either across supply or across the resistance. If the resistance is low, the voltmeters should be connected

A)

across the supply

B)

across the resistance

C)

either in two positions

D)

preferably across the supply

Correct Answer : across the resistance

Explaination : Since resistance is low current is high and voltage drop across ammeter is high. Therefore, voltmeter should be connected across resistance.

207 .

For measurement of surface temperature of solids the elements of RTD is usually in the shape of

A)

bar

B)

coil

C)

flat grid

D)

Either (A) or (B)

Correct Answer : flat grid

Explanation : The flat grid is attached to the surface of solid.

208 .

As per BIS, the number of accuracy classes of instrument is

A)

5

B)

6

C)

7

D)

8

Correct Answer : 8

Explanation : 8 losses.

209 .

In most of instruments, the controlling torque is provided by

A)

eddy current

B)

spring

C)

fluid fraction

D)

None of the above

Correct Answer : eddy current

Explanation : Eddy current damping is very common.

210 .

A 0-200 V voltmeter has a sensitivity of 1 kÎ© per volt. The resistance of voltmeter is

A)

1 kÎ©

B)

50 kÎ©

C)

100 kÎ©

D)

200 kÎ©

Correct Answer : 100 kÎ©

Explanation : 200 x 1 kΩ.

211 .

In electronic voltmeters the measuring device is a

A)

moving coil instrument

B)

moving iron instrument

C)

dynamometer instrument

D)

None of the above

Correct Answer : moving coil instrument

Explanation : The a.c. voltage is rectified and measured by PMMC instrument.

212 .

An ammeter has a resistance of 50 ohms and a shunt of 0.01 Î©. The deflection is Î¸. If the shunt resistance is increased to 0.02 Î©, the deflection will be.

A)

Î¸

B)

2Î¸

C)

0.5Î¸

D)

0.25Î¸

Correct Answer : 2Î¸

Explanation : Since shunt resistance is doubled, current through ammeter is doubled (current division for resistances in parallel). Therefore reading is 2 θ.

213 .

Which of the following measurements using a dc potentiometer do not require standardisation of potentiometer?

A)

Measurement of resistance

B)

Calibration of voltmeter

C)

Measurement of unknown voltage

D)

Measurement of unknown current

Correct Answer : Measurement of resistance

Explanation : Unknown resistance is compared with a standard resistance. Therefore standardisation of potentiometer is not necessary.

214 .

Which of the following statement is correct for two wattmeters method of power measurement in 3 phase circuit?

A)

When two wattmeters have equal readings power factor is 0.5.

B)

When power factor is 1, one of the wattmeters readings is zero

C)

When the two wattmeter read equal and opposite, p.f. is zero.

D)

Power can be measured by this method only for star connected loads

Correct Answer : When the two wattmeter read equal and opposite, p.f. is zero.

Explanation : When p.f. is zero, active power is zero and the two redaings are equal and opposite.

215 .

Induction wattmeter can be used in

A)

dc circuit only

B)

ac 3 phase only

C)

both ac and dc circuit

D)

ac circuit only

Correct Answer : ac circuit only

Explanation : Induction effect occurs with ac only.

216 .

A moving iron instrument gives correct reading when used at

A)

low frequencies

B)

high frequencies

C)

only one frequency

D)

all frequencies upto a certain value

Correct Answer : only one frequency

Explanation : If frequency changes reactance of coil changes and reading is affected.

217 .

In a thermocouple temperature transducer, the output voltage is usually measured by

A)

high resistance ammeter

B)

high resistance milli-voltmeter

C)

high resistance voltmeter

D)

None of the above

Correct Answer : high resistance milli-voltmeter

Explanation : The output voltage is very small. So we need a milli voltmeter.

218 .

A dynamometer wattmeter is connected in ac circuit. The measured power is

A)

average power

B)

rms power

C)

peak power

D)

instantaneous power

Correct Answer : average power

Explanation : All wattmeters measure average power over a cycle.

219 .

In two wattmeter method of 3 phase power measurement, when does one wattmeter read negative

A)

when power factor is unity

B)

when power factor is less than 0.5

C)

when power factor is less than 0.5 lagging

D)

when power factor is greater than 0.5 lagging

Correct Answer : when power factor is less than 0.5

Explanation : When p.f. is less than 0.5 (leading or lagging) one of the wattmeters reads negative.

220 .

The multiplier and the meter coil in a voltmeter are in

A)

Series

B)

Parallel

C)

Series-parallel

D)

None of the above

Correct Answer : Series

221 .

Wagner earthing device is used to eliminate errors due to

A)

Electrostatic coupling

B)

Electromagnetic coupling

C)

Both (A) and (B)

D)

None of the above

Correct Answer : Electrostatic coupling

222 .

A mulliammeter can be used as

A)

Ohmmeter

B)

Wattmeter

C)

Frequency meter

D)

Voltmeter and ammeter

Correct Answer : Voltmeter and ammeter

223 .

The EMF of Weston standard cell is measured using

A)

Digital Volt meter

B)

Potentiometer

C)

Moving-coil meter

D)

Moving- iron meter

Correct Answer : Potentiometer

224 .

A resistor of 10 kΩ with 5% tolerance is connected in parallel with a 5 kΩ resistor of 10% tolerance. What is the tolerance limit for the parallel network?

A)

5%

B)

6.67%

C)

8.33%

D)

10%

Correct Answer : 8.33%

225 .

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

A)

Supply voltage is low

B)

Load impedance is low

C)

Both (A) and (B)

D)

Load impedance is high

Correct Answer : Load impedance is high

226 .

Some wire- wound resistors have bifilar winding. This type of winding is used to

A)

Reduce the tolerance

B)

Increase the thermal stability

C)

Reduce the inductance of winding

D)

Double the power rating of the resistor

Correct Answer : Reduce the inductance of winding

227 .

A permanent magnet moving coil ammeter has a coil resistance of 99ohm and Full Scale DeflectionFSD. current of 0.1mA. Shunt resistance is 1 ohm. Current through the meter at 0.5 F.S.D is

A)

B)

0.1mA

C)

0.023mA

D)

0.05mA

Correct Answer : 0.05mA

228 .

The chemical effect of current is used in

A)

D.C. ammeter

B)

D.C. energy meter

C)

D.C. ammeter hour meter

D)

None of the above

Correct Answer : D.C. ammeter hour meter

229 .

The form factor in AC is the ratio of

A)

Peak value to rms value

B)

Peak value to average value

C)

Rms value to peak value

D)

Rms value to average value

Correct Answer : Rms value to average value

230 .

The error of an instrument is normally given as a percentage of

A)

Full-scale value

B)

Rms value

C)

Mean value

D)

Measured value

Correct Answer : Full-scale value

231 .

Electrostatic instruments are normally used for

A)

Low voltage measurements

B)

High voltage measurements

C)

Low current measurements

D)

High current measurements

Correct Answer : High voltage measurements

232 .

An instrument to be used for measurement and control should preferably have

A)

Non-linear output

B)

A highly damped response

C)

Dead zone and dead time

D)

Linear output and fast response

Correct Answer : Linear output and fast response

233 .

Which of the following devices should be used for accurate measurement of low D.C. voltage?

A)

D.C. potentiometer

B)

Small range moving coil voltmeter

C)

Small range thermocouple voltmeter

D)

None of the above

Correct Answer : D.C. potentiometer

234 .

Which meter is suitable for the measurement of 10mV at 50MHz?

A)

CRO

B)

VTVM

C)

Moving iron voltmeter

D)

Moving coil voltmeter

Correct Answer : CRO

235 .

The repeat accuracy of an instrument can be judged from its

A)

Static error

B)

Linearity error

C)

Dynamic error

D)

Standard deviation of error

Correct Answer : Standard deviation of error

236 .

The resistance offered to the passage of an in-varying current by a column of mercury at the temperature of melting ice of mass 14.4521 gms of uniform cross-sectional area and length 106.3cm is

A)

Standard ohm

B)

One international ohm

C)

One ohm according to SI units

D)

One ohm according to working standards

Correct Answer : One international ohm

237 .

In a gravity controlled instrument, the deflection angle is proportional

A)

Measurand

B)

Sine of the measurand

C)

Sine inverse of measurand

D)

Square of the measurand

Correct Answer : Sine inverse of measurand

238 .

The problem of Electrostatic coupling in a transformer is acute at

A)

Low frequencies

B)

High frequencies

C)

Power frequencies

D)

High load on the transformer

Correct Answer : High frequencies

239 .

Increasing secondary burden _____________

A)

increases I_s

B)

decreases I_p

C)

ecreases I_s

D)

keeps I_s constant

Correct Answer : increases I_s

Explaination : When the secondary burden of a potential transformer increases, it leads to an increase in the secondary current. As a result the primary current also increases.

240 .

Which of the following device is used to measure power in A.C. circuits?

A)

ammeter

B)

wattmeter

C)

voltmeter

D)

ohmmeter

Correct Answer : voltmeter

Explanation : A.C. circuits make use of power factor of the circuit in addition to the current flowing through the circuit and the voltage across the circuit. As a result, a wattmeter is used to measure A.C. power.

241 .

When the moving coil in a Dynamometer type wattmeter deflects ________

A)

current flows

B)

pointer moves

C)

voltage is generated

D)

pointer doesnâ€™t move

Correct Answer : pointer moves

Explanation : In a Dynamometer type wattmeter, when the moving coil deflects the pointer moves over the scale. The pointer then comes back to rest at a point where the deflecting torque equals the controlling torque.

242 .

What is the effect of capacitance on wattmeter reading?

A)

aiding the inductance

B)

aiding the capacitance

C)

opposite to that of inductance

D)

opposite to that of resistance

Correct Answer : opposite to that of inductance

Explanation : For lagging power factor of the load, the wattmeter reading is more. As a result, the wattmeter shows a reading opposite to that of the inductance.

243 .

Which of the following compares the output in a successive approximation type DVM?

A)

diode

B)

rectifier

C)

op amp

D)

comparator

Correct Answer : comparator

Explanation : A comparator is used to compare the output of the digital to analog converter in a successive approximation type DVM. As a result the comparator provides high or low signals.

244 .

Which of the following is the main device used in the linear ramp technique?

A)

linear ramp

B)

non-linear ramp

C)

asymptotic ramp

D)

exponential ramp

Correct Answer : linear ramp

Explanation : The linear ramp technique essentially consists of a linear ramp. It is either positive or negative going. Range of the linear ramp varies from –12 V to +12 V. Base range varies from –10 V to +10 V.

245 .

Which of the following determines the rate of measurement cycles?

A)

amplifier

B)

oscillator

C)

oscilloscope

D)

multivibrator

Correct Answer : oscilloscope

Explanation : Initiation of the measurement cycles is taken care of by the sample rate multivibrator. This vibrator oscillates at the rate of 1000 cycles per second. It is adjusted by a front panel control.

246 .

Which of the following determines light intensity in a CRT?

A)

voltage

B)

current

C)

fluorescent screen

D)

momentum of electrons

Correct Answer : momentum of electrons

Explanation : Momentum of the electrons gives the intensity or brightness of the light emitted from the fluorescent screen due to electron bombardment. It is given as the product of the no of electrons and their speed.

247 .

Which of the following technique of a Dual Trace Oscilloscope maintains the phase between the signals?

A)

Chop mode

B)

Alternate mode

C)

Analog mode

D)

Mixed mode

Correct Answer : Alternate mode

Explanation : In a Dual Trace Oscilloscope, the alternate mode of operation enables to maintain the correct phase relationship between the signals from the channels A and B.

248 .

Which of the following oscilloscope is used in a digital storage oscilloscope?

A)

modern

B)

conventional

C)

dual trace

D)

multi trace

Correct Answer : conventional

Explanation : A digital storage oscilloscope makes use of a conventional cathode ray tube. As a result, the cost is reduced.

249 .

The full-scale deflection current of an ammeter is 1 mA and its internal resistance is 100 ohms. This is to have full deflection when 100V is measured. What is the value of series resistor to be used?

A)

99.99 ohms

B)

100 ohms

C)

99.99 K ohms

D)

100 K ohms

Correct Answer : 99.99 K ohms

250 .

A spring controlled indicating instrument has a deflection of 90° for maximum current I. The corresponding deflection for a gravity controlled instrument is

A)

0°

B)

30°

C)

90°

D)

120°

Correct Answer : 30°

251 .

PMMC type instruments normally use

A)

Air friction damping

B)

Fluid friction damping

C)

Eddy current damping

D)

None of the above

Correct Answer : Eddy current damping

252 .

Jewels are used in instruments for the purpose of

A)

Bearing

B)

Damping

C)

Torque control

D)

Suppressing noise

Correct Answer : Bearing

253 .

Which instrument has identical calibration for ac as well as dc values?

A)

Induction type

B)

Hot wire type

C)

Moving coil type

D)

Moving iron type

Correct Answer : Hot wire type

254 .

If the instrument is to have a wide range, the instrument should have

A)

Linear scale

B)

Square-law scale

C)

Exponential scale

D)

Logarithmic scale

Correct Answer : Logarithmic scale

255 .

It can be stated that

A)

CT operates with a higher flux density than PT

B)

CT operates at almost the same flux density as a PT

C)

CT operates with considerably lower flux density than a PT

D)

No generalisation can be made with regard to the flux densities in CT and PT

Correct Answer : CT operates with considerably lower flux density than a PT

256 .

With a sweep time 10ms across the screen the approx. horizontal sawtooth frequency will be

A)

1kHz

B)

50Hz

C)

100Hz

D)

500Hz

Correct Answer : 100Hz

257 .

To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken

A)

From a battery

B)

From the same source as the unknown voltage

C)

From a source which is not the same as the unknown voltage

D)

None of the above

Correct Answer : From the same source as the unknown voltage

258 .

The thermocouple instruments do not have

A)

High degree of measuring accuracy

B)

High sensitivity

C)

Absence of frequency error

D)

Independence of ambient temperature

Correct Answer : High degree of measuring accuracy

259 .

Which of the following instruments can be used to measure AC current only?

A)

Moving iron voltmeter

B)

Induction type ammeter

C)

Moving iron ammeter

D)

Permanent Magnet Type ammeter

Correct Answer : Induction type ammeter

260 .

Wien bridge is useful for measuring

A)

Medium frequency

B)

Low frequency

C)

Very high frequency

D)

High frequency

Correct Answer : High frequency

261 .

Magnetic effect of current is used in

A)

ammeters

B)

voltmeters

C)

wattmeters

D)

ammeters, voltmeters, wattmeters and energy meters

Correct Answer : ammeters, voltmeters, wattmeters and energy meters

262 .

Heating effect of current is used in

A)

ammeters

B)

voltmeters

C)

Both (A) and (B)

D)

wattmeters

Correct Answer : Both (A) and (B)

263 .

The Y plates of a CRO are excited by a voltage 2 sin 100 t and the X plates are not connected. The display would be

A)

slant line

B)

sine wave

C)

a vertical line

D)

a horizontal line

Correct Answer : a vertical line

264 .

Which of these instruments is dynamometers type?

A)

Wattmeter

B)

Power factor meter

C)

Frequency meter

D)

Both (A) and (B)

Correct Answer : Both (A) and (B)

265 .

It is required to measure temperature in the range of 1300-1520Â°C. The most suitable thermocouple is

A)

iron constantan

B)

platinum-rhodium

C)

chromel aluminium

D)

chromel constantan

Correct Answer : platinum-rhodium

266 .

An ammeter is_______

A)

absolute instrument

B)

secondary instrument

C)

recording instrument

D)

integrating instrument

Correct Answer : secondary instrument

267 .

The instrument used to check insulation of household wiring is

A)

megger

B)

ohmmeter

C)

multimeter

D)

high resistance voltmeter

Correct Answer : megger

268 .

The channel required for FM telemetry is

A)

same as required for AM telemetry

B)

smaller than that required by AM telemetry

C)

10 times that required for AM telemetry

D)

100 times that required for AM telemetry

Correct Answer : 100 times that required for AM telemetry

269 .

A digital voltmeter can count from 0 to 9999. If full scale reading is 9.999 V, the resolution of full scale reading is

A)

0.001

B)

1 mV

C)

2 digit

D)

1000

Correct Answer : 1 mV

270 .

The most serious problems in ac bridge measurement is

A)

stray fields

B)

eddy currents

C)

leakage current

D)

residual magnetism

Correct Answer : stray fields

271 .

The pointer of an indicating instrument should be

A)

heavy

B)

very heavy

C)

very light

D)

neither heavy nor light

Correct Answer : very light

272 .

The resistance of resistance strain gauge is about

A)

0.5 Î©

B)

5 Î©

C)

50 Î©

D)

120 Î©

273 .

Which bridge can be used to measure frequency?

A)

Wein

B)

Kelvin

C)

Maxwell

D)

Schering

Correct Answer : Wein

274 .

The time base generator in a CRO gives an output which is

A)

high frequency sinusoidal

B)

high frequency sawtooth

C)

low frequency sinusoidal

D)

low frequency rectangular

Correct Answer : high frequency sawtooth

275 .

In low power factor wattmeter, the compensating coil is connected

A)

in series with current coil

B)

in series with pressure coil

C)

in parallel with current coil

D)

in parallel with pressure coil

Correct Answer : in series with pressure coil

276 .

An average responding rectifier type electronic voltmeter has its scale calibrated in terms of rms value of sine wave. If 100 V peak value square wave is fed to this voltmeter, the reading will be

A)

70.7 V

B)

90.9 V

C)

100 V

D)

111 V

Correct Answer : 111 V

277 .

LVDT is used to measure

A)

pressure

B)

temperature

C)

displacement

D)

Any of the above

Correct Answer : displacement

278 .

Absolute instruments are used in

A)

industries

B)

laboratories

C)

power houses

D)

standard laboratories

Correct Answer : standard laboratories

279 .

Burden of an instrument transformer is expressed in

A)

A

B)

Î©

C)

V-A

D)

watt

Correct Answer : V-A

280 .

Which of the following devices should be used for accurate measurement of a low dc voltage?

A)

Dc potentiometer

B)

Hot wire instrument

C)

Small range moving coil voltmeter

D)

Small range thermocouple voltmeter

Correct Answer : Dc potentiometer

281 .

An electrodynamometer instrument has the advantage of

A)

low cost

B)

high torque/weight ratio

C)

freedom from hysteresis and eddy currents because air cored coils are used

D)

freedom from hysteresis and eddy currents because cores of coils have special ferromagnetic material

Correct Answer : freedom from hysteresis and eddy currents because air cored coils are used

282 .

A Q meter uses the principle of

A)

variation of self inductance

B)

series resonance

C)

variation of mutual inductance

D)

None of the above

Correct Answer : series resonance

283 .

In semiconductor strain gauge

A)

resistance increases with strain

B)

resistance decreases with strain

C)

resistance increases with strain in n type and decreases with strain in p type

D)

resistance increases with strain in p type and decreases with strain in n type

Correct Answer : resistance increases with strain in p type and decreases with strain in n type

284 .

Which of the following is not a transducer in true sense?

A)

LCD

B)

Piezo electric

C)

Thermocouple

D)

Photo electric cell

Correct Answer : LCD

285 .

Four terminal approach is used in measuring low resistance because it

A)

eliminates stray capacitance

B)

eliminates stray inductance

C)

eliminates thermoelectric energy

D)

eliminates the effect of leads and contacts

Correct Answer : eliminates the effect of leads and contacts

286 .

In Weston synchronoscope the fixed coils are connected across

A)

lamp

B)

bus bars

C)

incoming alternator

D)

Either (A) or (B)

Correct Answer : incoming alternator

287 .

The output of a Piezoelectric crystal has

A)

low amplitude and low impedance

B)

low amplitude and high impedance

C)

high amplitude and low impedance

D)

high amplitude and high impedance

Correct Answer : low amplitude and high impedance

288 .

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

A)

voltage is low

B)

voltage is high

C)

load impedance is low

D)

load impedance in high

Correct Answer : load impedance in high

289 .

A universal RLC bridge uses

A)

Maxwell bridge for measurement of inductance and De Sauty's bridge for measurement of capacitance

B)

Maxwell Wien bridge for measurement of inductance and Wien bridge for measurement of capacitance

C)

Maxwell Wien bridge for measurement of inductance and modified De Sauty bridge for measurement of inductance

D)

Maxwell's bridge for measurement of inductance and modified De Sauty bridge for measurement of capacitance

Correct Answer : Maxwell Wien bridge for measurement of inductance and modified De Sauty bridge for measurement of inductance

290 .

The operating voltage of a megger is about

A)

100 V

B)

12 V

C)

6 V

D)

1 V

Correct Answer : 100 V

291 .

Capacitive transducer is superior to inductive type for measurement of capacitance because of

A)

small size

B)

high accuracy

C)

absence of non-linearity

D)

high frequency response

Correct Answer : high frequency response

292 .

Which of the following effects is used in measurement of magnetic flux?

A)

Seeback effect

B)

Hall effect

C)

Piezo electric effect

D)

Photoelectric effect

Correct Answer : Hall effect

293 .

Loading effect is primarily caused by instruments having

A)

low sensitivity

B)

high range

C)

high resistance

D)

high sensitivity

Correct Answer : low sensitivity

294 .

An ohmmeter is a______

A)

induction instrument

B)

moving iron instrument

C)

moving coil instrument

D)

dynamometer instrument

Correct Answer : moving coil instrument

295 .

Which of the following is active transducer?

A)

Photoelectric

B)

Photovoltaic

C)

Photoemissive

D)

Photoconductive

Correct Answer : Photovoltaic

296 .

Which is the displacement transducer with excellent sensitivity, linearity and resolution?

A)

LVDT

B)

Strain gauge

C)

Absolute encoder

D)

Incremental encoder

Correct Answer : LVDT

297 .

In a current transformers

A)

the number of turns in primary and secondary windings are nearly equal

B)

the number of secondary turns is very small as compared to the number of primary turns

C)

Both (A) and (B)

D)

the number of primary turns is very small as compared to number of secondary turns.

Correct Answer : the number of primary turns is very small as compared to number of secondary turns.

298 .

The time base of a high frequency CRO whose screen diameter is 10 cm is set at 10 μ sec/cm. The lowest frequency which can be fully displayed on the screen is

A)

equal to 10 kHz

B)

less than 10 kHz

C)

equal to 100 kHz

D)

more than 100 kHz

Correct Answer : equal to 10 kHz

299 .

Gauge factor of a strain gauge is_________

A)

change in resistance per unit change in length

B)

unit change in length per unit change in resistance

C)

unit change in resistance per unit change in length

D)

None of the above

Correct Answer : unit change in resistance per unit change in length

300 .

A dynamometer wattmeter can be used for

A)

dc only

B)

ac only

C)

dc and 50 Hz ac

D)

dc and high frequency ac

Correct Answer : dc and 50 Hz ac

301 .

A direct current can be measured

A)

directly by dc potentiometer

B)

by dc potentiometer in conjunction with a standard resistance

C)

by dc potentiometer in conjunction with volt ratio box

D)

None of the above

Correct Answer : by dc potentiometer in conjunction with a standard resistance

302 .

A data signal having frequency components from dc to 50 Hz is to be sent through pulse code modulation using an 8 digit code. The minimum carrier channel bandwidth is

A)

8 kHz

B)

4 kHz

C)

2 kHz

D)

1 kHz

Correct Answer : 4 kHz

303 .

A moving iron instrument has

A)

two iron vanes, one fixed and one movable

B)

two movable iron vanes

C)

two aluminium vanes, one fixed and one movable

D)

two vanes, one fixed made of Aluminium and the other movable made of iron

Correct Answer : two iron vanes, one fixed and one movable

304 .

The temperature coefficient of resistance for a thermistor is

A)

low and positive

B)

low and negative

C)

high and positive

D)

high and negative

Correct Answer : high and negative

305 .

A linear displacement digital transducer generally uses

A)

BCD

B)

gray code

C)

hexadecimal code

D)

straight binary code

Correct Answer : gray code

306 .

To measure an unknown ac voltage by an ac potentiometer it is desirable that supply for the potentiometer is taken

A)

from a battery

B)

from a source which is not the same as unknown voltage

C)

from the same source as the unknown voltage

D)

Either (A) or (B)

Correct Answer : from the same source as the unknown voltage

307 .

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

A)

balanced loads

B)

unbalanced loads

C)

star connected loads

D)

both balanced and unbalanced loads

Correct Answer : both balanced and unbalanced loads

308 .

A coil resonates at 1 MHz with a resonating capacitance of 72 pF. At 500 pF, resonance is obtained with a resonating capacitor of 360 pF. The self capacitance of coil is

A)

12 pF

B)

24 pF

C)

30 pF

D)

72 pF

Correct Answer : 24 pF

309 .

A resistance strain gauge has a resistance of about

A)

1 Î©

B)

10 Î©

C)

25 Î©

D)

100 Î©

310 .

A Weston frequency meter is

A)

moving iron instrument

B)

induction instrument

C)

moving coil instrument

D)

dynamometer instrument

Correct Answer : moving iron instrument

311 .

The 10 MHz in the specification of CRO means that

A)

the vertical amplifier has been designed for 10 MHz

B)

the sweep frequency is 10 MHz

C)

the frequency of input signal should not be more than 10 MHz

D)

None of the above

Correct Answer : the sweep frequency is 10 MHz

312 .

In which of the following method of acquisition, pretrigger event is lost?

A)

Analog Sampling

B)

Real time sampling

C)

Sequential repetitive sampling

D)

Random repetitive sampling

Correct Answer : Sequential repetitive sampling

Explanation : In Sequential repetitive sampling, pretrigger information cannot be captured. And the pretrigger view is lost. It can be used only in microwave digital oscilloscope as a result.

313 .

Which of the following is the main function of auxiliary equipment?

A)

ramp response

B)

linear response

C)

unit step response

D)

non-linear response

Correct Answer : linear response

Explanation : The typical functions of auxiliary equipments include linearization and limit compression for the input signals. Individual instruments or a digital computer is used to perform these functions.

314 .

Which of the following is the main objective of process control?

A)

to control optical parameters

B)

to control electrical parameters

C)

to control mechanical parameters

D)

to control physical parameters

Correct Answer : to control physical parameters

Explanation : Process control is mainly used in order to control the physical parameters including temperature, pressure, flow rate, force, etc.

315 .

Which of the following technique is most widely used in the single channel data acquisition system?

A)

Successive approximation

B)

Flash approximation

C)

Delta Sigma approximation

D)

Counter type approximation

Correct Answer : Successive approximation

Explanation : The successive approximation technique is most widely used in a single channel data acquisition system. This is due to the fact that it has a high value of resolution and high speed.

316 .

Which of the following is the best example of a single-channel data acquisition system?

A)

APM

B)

BPM

C)

CPM

D)

DPM

Correct Answer : DPM

Explanation : A digital panel meter usually abbreviated as DPM is the best example of a single channel data acquisition system.

317 .

Which of these instruments has highest power consumption?

A)

Moving coil

B)

Electrostatic

C)

Hot wire

D)

Dynamometer

Correct Answer : Hot wire

318 .

If A = 629 ± 8 and B = 131 ± 3, A - B with range of doubt is

A)

498 ± 4

B)

498 ± 8

C)

498 ± 11

D)

498 ± 13

Correct Answer : 498 ± 11

319 .

A vibration galvanometer is a

A)

induction instrument

B)

moving coil instrument

C)

moving iron instrument

D)

dynamometer instrument

Correct Answer : moving coil instrument

320 .

A power factor meter has_____

A)

one current and one pressure circuit

B)

two current circuits and one pressure circuit

C)

one current circuit and two pressure circuits

D)

two current circuits and two pressure circuits

Correct Answer : one current circuit and two pressure circuits

321 .

In a semiconductor strain gauge, the ohmic electrical contacts are generally made of

A)

gold wire

B)

nickel wire

C)

copper wire

D)

aluminium wire

Correct Answer : gold wire

322 .

To measure dielectric loss you would use

A)

Kelvin bridge

B)

Schering bridge

C)

Anderson bridge

D)

Maxwell's bridge

Correct Answer : Schering bridge

323 .

Minute cracks in metals and minute faults in welded joints can be detected using

A)

a rays

B)

IR rays

C)

UV rays

D)

X-ray/Î³-rays

Correct Answer : X-ray/Î³-rays

324 .

In a hot wire instrument, the deflection is proportional to

A)

peak value of ac current

B)

rms value of ac current

C)

average value of ac current

D)

None of the above

Correct Answer : peak value of ac current

325 .

If temperature increases by about 50Â°, the resistance of thermistor changes to

A)

half of its initial value

B)

twice of its initial value

C)

one eight of its initial value

D)

eight times of its initial value

Correct Answer : one eight of its initial value

326 .

Which of the following draws minimum power from source?

A)

PMMC

B)

Electronic voltmeter

C)

Moving iron voltmeter

D)

Electrostatic voltmeter

Correct Answer : Electronic voltmeter

327 .

Acoustic strain gauges

A)

do not have long term stability

B)

have good linearity of measurement

C)

have a large range of measurement

D)

have an accuracy range of 0.1-1% depending on environment

Correct Answer : have an accuracy range of 0.1-1% depending on environment

328 .

A permanent magnet moving coil measures

A)

dc value

B)

peak value

C)

true rms value

D)

rms plus dc value

Correct Answer : dc value

329 .

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

A)

all coils are in parallel

B)

the coils are in series-parallel

C)

all the coils are in series

D)

None of the above

Correct Answer : all the coils are in series

330 .

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

A)

compensate for error in voltmeter

B)

compensate for change in temperature

C)

compensate for resistance of strain gauge

D)

compensate for error due to change in voltage of battery

Correct Answer : compensate for change in temperature