120+ Electromagnetic Interference Solved MCQs

1.

Moving Iron instruments can be used on:

A. ac and dc both
B. ac only
C. dc only
D. none of the above
Answer» A. ac and dc both
2.

In spring control instruments, controlling torque:

A. can be adjusted easily
B. cannot be adjusted easily
C. remains the same
D. varies with the load
Answer» B. cannot be adjusted easily
3.

Chemical effect is used for the operation of:

A. voltmeter
B. ammeter
C. ampere hour meter
D. kwh meter
Answer» C. ampere hour meter
4.

The deflection torque can be produced by:

A. gravity control
B. spring control
C. air friction
D. magneitcally
Answer» D. magneitcally
5.

Moving coil instruments are:

A. permanent magnet type
B. dynamometer type
C. induction type
D. permanent magnet and dynamometer type
Answer» D. permanent magnet and dynamometer type
6.

For increasing the range of an ammeter, connect:

A. a high value resistance in series with the ammeter coil
B. a high value resistance in parallel with the ammeter coil
C. a low value resistance in parallel with the ammeter coil
D. a low value resistance in series with the ammeter coil
Answer» C. a low value resistance in parallel with the ammeter coil
7.

A galvanometer can be used for measuring current and voltage of a circuit by:

A. shunt only
B. connecting high value of resistance in series only
C. shunt for measuring current and high resistance in series for voltage
D. without shunt and series resistance
Answer» C. shunt for measuring current and high resistance in series for voltage
8.

The energy consumption of MI instrument as compared to MC instrument is:

A. same
B. more
C. less
D. very small
Answer» B. more
9.

An ammeter requires a change of 4A in its coil to produce a pointer deflection of 8mm then its sensitivity is

A. 2.5 mm/a
B. 2.0 mm/a
C. 0.5 mm/a
D. none of the above
Answer» B. 2.0 mm/a
10.

Electrostatic type instruments are mainly used for measurement of

A. heavy currents
B. low currents
C. low voltages
D. high voltages
Answer» D. high voltages
11.

Measurement range of a voltmeter can be extended by using:

A. high current resistance
B. high series resistance
C. low shunt resistance
D. low series resistance
Answer» B. high series resistance
12.

Which of the following voltmeter have least power consumption:

A. moving iron
B. hot-wire
C. electrostatic
D. induction type
Answer» C. electrostatic
13.

Which of the following instruments have least torque/weight ratio:

A. dynamometer type
B. pmmc
C. attraction type moving iron
D. repulsion type moving iron
Answer» A. dynamometer type
14.

Fluid friction damping can be used in

A. horizontally mounted instruments
B. vertically mounted instruments
C. both horizontally mounted instruments and vertically mounted instruments
D. none of the above
Answer» B. vertically mounted instruments
15.

The ratio and phase angle errors in potential transformer may be reduced by

A. increasing the exciting current
B. increasing the resistance and leakage reactance in the transformer
C. by not employing turns compensation
D. none of the above
Answer» D. none of the above
16.

A voltmeter should have

A. . low internal resistance
B. . high internal resistance
C. . electrostatic plates
D. . a sensitive amplifier
Answer» B. . high internal resistance
17.

The major advantage of electromagnet type meter over a permanent magnet meter is

A. . the electromagnet meter costs much less
B. the permanent magnet meter has a more sluggish coil
C. . the electromagnet meter need not be aligned with the earth’s magnetic field
D. . the electromagnet meter is more rugged
Answer» D. . the electromagnet meter is more rugged
18.

The change in the direction of a compass needle, when a current carrying wire is brought near, is called

A. . electromagnetic deflection
B. . electroscopic force
C. magnetic force
D. . electrostatic force
Answer» A. . electromagnetic deflection
19.

The use of _____ instruments is merely confined within laboratories as standardizing instruments.

A. absolute
B. indicating
C. recording
D. integrating
Answer» A. absolute
20.

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. absolute instruments
B. indicating instruments
C. recording instruments
D. integrating instruments
Answer» B. indicating instruments
21.

_____ instruments are those which measure the total quantity of electricity delivered in a particular time.

A. absolute
B. indicating
C. recording
D. integrating
Answer» D. integrating
22.

Which of the following are integrating instruments ?

A. ammeters
B. voltmeters
C. wattmeters
D. ampere-hour and watt-hour meters
Answer» D. ampere-hour and watt-hour meters
23.

Which of the following essential features is possessed by an indicating instrument ?

A. deflecting device
B. controlling device
C. damping device
D. all of the above
Answer» D. all of the above
24.

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

A. deflecting
B. controlling
C. damping
D. any of the above
Answer» C. damping
25.

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

A. should be non-magnetic
B. most be of low temperature co-efficient
C. should have low specific resistance
D. all of the above
Answer» D. all of the above
26.

Which of the following properties a damping oil must possess ?

A. must be a good insulator
B. should not have corrosive action upon the metal of the vane
C. the viscosity of the oil should not change with the temperature
D. all of the above
Answer» D. all of the above
27.

Which of the following devices may be used for extending the range of instruments ?

A. shunts
B. multipliers
C. current transformers
D. all of the above
Answer» D. all of the above
28.

For handling greater currents induction wattmeters are used in conjunction with

A. potential transformers
B. current transformers
C. power transformers
D. either of the above
Answer» B. current transformers
29.

The pointer of an indicating instrument should be

A. very light
B. very heavy
C. either (a) or (b)
D. neither (a) nor (b)
Answer» A. very light
30.

In majority of instruments damping is provided by

A. fluid friction
B. spring
C. eddy currents
D. all of the above
Answer» C. eddy currents
31.

An ammeter is a

A. secondary instrument
B. absolute instrument
C. recording instrument
D. integrating instrument
Answer» A. secondary instrument
32.

In a portable instrument, the controlling torque is provided by

A. spring
B. gravity
C. eddy currents
D. all of the above
Answer» A. spring
33.

The desirable static characteristics of a measuring system are

A. accuracy and reproducibility
B. accuracy, sensitivity and reproducibility
C. drift and dead zone
D. static error
Answer» B. accuracy, sensitivity and reproducibility
34.

The ratio of maximum displacement deviation to full scale deviation of the instrument is called

A. static sensitivity
B. dynamic deviation
C. linearity
D. precision or accuracy
Answer» C. linearity
35.

Systematic errors are

A. instrumental errors
B. environmental errors
C. observational errors
D. all of the above
Answer» D. all of the above
36.

The gravity controlled instrument has crowded scale because current is proportional to

A. balancing weight
B. deflection angle
C. sine of deflection angle
D. none of the above
Answer» C. sine of deflection angle
37.

Instrument transformers are

A. potential transformers
B. current transformers
C. both (a) and (b)
D. power transformers
Answer» C. both (a) and (b)
38.

The damping force acts on the moving system of an indicating instruments only when it is

A. moving
B. stationary
C. near its full scale deflection
D. just staring to move
Answer» A. moving
39.

A moving iron ammeter coil has few turns of thick wire in order to have:

A. high sensitivity
B. effective damping
C. low resistance and large current carrying capacity
D. large scale
Answer» C. low resistance and large current carrying capacity
40.

Swamping of resistance is used to compensate error due to:

A. stray magnetic field
B. temperature variations
C. large supply variations
D. none of the above
Answer» B. temperature variations
41.

The turns ratio for C.T. is defined as

A. n2/n1
B. n1/n2
C. (n1+n2)/n1
D. (n1+n2)/n2
Answer» A. n2/n1
42.

A 3810/63 P.T. is used with a voltmeter gives reading of 28.11 V , then the actual line voltage is ------ V

A. 0.4648
B. 975
C. 1700
D. 1100
Answer» C. 1700
43.

A 1000:5 C.T. is used with an ammeter. If ammeter reading is 1.8 A then the actual line current is --------------A

A. 160
B. 400
C. 0.09
D. 360
Answer» D. 360
44.

While testing cables the galvanometer used should be initially short-circuited in order to protect it from sudden initial inrush currents as the cable have:

A. a low value of initial resistance
B. a low value of initial capacitance
C. a high value of initial capacitance
D. both (a) and (b)
Answer» C. a high value of initial capacitance
45.

A megger indicates infinity when test terminals are open-circuited. This is because:

A. no current flows through the current coil
B. no current flows through the pressure coil
C. no current flows through the compensating winding
D. current does not flow through current coil and pressure coil
Answer» A. no current flows through the current coil
46.

Potentiometer is an __ instrument:

A. indicating
B. comparison
C. calibrating
D. recording
Answer» B. comparison
47.

Which of the following bridge is frequency sensitive:

A. wheatstone bridge
B. maxwell bridge
C. anderson bridge
D. wien bridge
Answer» C. anderson bridge
48.

The size of the earth or ground wire is based on the:

A. maximum fault current carrying through the ground wire
B. rated current carrying capacity of the service line
C. depends on the soil resistance
D. both (a) and (c)
Answer» D. both (a) and (c)
49.

Earth wire or ground wire is made of:

A. copper
B. aluminium
C. iron
D. galvanized steel
Answer» D. galvanized steel
50.

Average resistance of human body is:

A. 500 ohms
B. 1000 ohms
C. 1500 ohms
D. 2000 ohms
Answer» B. 1000 ohms
51.

Generally grounding is provided for:

A. only for the safety of the equipment
B. only for the safety of the operating personnel
C. both (a) and (b)
D. none of the above
Answer» C. both (a) and (b)
52.

Ground resistance should be designed such that:

A. grounding resistance should be as low as possible
B. grounding resistance should be as high as possible
C. grounding resistance should be always zero
D. none of the above
Answer» A. grounding resistance should be as low as possible
53.

The objective of earthing or grounding is:

A. to provide as low resistance possible to the ground
B. to provide as high resistance possible to the ground
C. to provide flow of positive, negative and zero sequence currents
D. none of the above
Answer» A. to provide as low resistance possible to the ground
54.

The vale of resistance of an earthing electrode depends upon

A. shape and material of the electrode
B. depth to which electrode is driven into earth
C. specific resistance of soil
D. all of the above.
Answer» D. all of the above.
55.

A bridge circuit works at a frequency of 2KHz, the following can be used as detectors for detection of null conditions in the bridge:

A. vibration galvanometers and headphones
B. headphones and tunable amplifiers.
C. vibration galvanometers and tunable amplifiers.
D. vibration galvanometers, headphones and tunable amplifiers.
Answer» B. headphones and tunable amplifiers.
56.

Maxwell’s inductance capacitance bridge is used for measurement of inductance of:

A. low q coils
B. medium q coils
C. low and medium q coils
D. none of the above.
Answer» B. medium q coils
57.

The wheatstone bridge cant be used for precision measurements because errors are introduce into on account of :

A. resistance of connecting leads
B. thermo electric emf
C. contact resistances
D. all of the above.
Answer» D. all of the above.
58.

High resistances are provided with a guard terminal. This guard terminal is used to :

A. bypass leakage current
B. guard the resistance against stray electrostatic fields
C. guard the resistance against over loads.
D. none of the above.
Answer» A. bypass leakage current
59.

A potentiometer may be used for

A. measurement of resistance
B. measurement of current
C. calibration of voltmeter
D. all of the above
Answer» D. all of the above
60.

--------- is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another,

A. tangent galvanometer
B. meggar
C. current transformer
D. none of the above
Answer» B. meggar
61.

For measuring a very high resistance we should use

A. kelvin\s double bridge
B. wheat stone bridge
C. meggar
D. none of the above
Answer» C. meggar
62.

The electrical power to a meggar is provided by

A. battery
B. permanent magnet d.c. generator
C. ac. generator
D. any of the above
Answer» B. permanent magnet d.c. generator
63.

In a meggar controlling torque is provided by

A. spring
B. gravity
C. coil
D. eddy current
Answer» C. coil
64.

The operating voltage of a meggar is about

A. 6 v
B. 12 v
C. 40 v
D. 100 v
Answer» D. 100 v
65.

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

A. small range moving coil voltmeter
B. d.c. potentiometer
C. small range thermocouple voltmeter
D. none of the above
Answer» B. d.c. potentiometer
66.

It is required to measure the true open circuit e.m.f. of a battery. The best device is

A. d.c. voltmeter
B. ammeter and a known resistance
C. d.c. potentiometer
D. none of the above
Answer» C. d.c. potentiometer
67.

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

A. known inductance and resistance
B. known capacitance and resistance
C. known resistance
D. known inductance
Answer» B. known capacitance and resistance
68.

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

A. 10°
B. 80°
C. 120°
D. 170°
Answer» A. 10°
69.

To avoid the effect of stray magnetic field in A.C. bridges we can use

A. magnetic screening
B. wagner earthing device
C. wave filters
D. any of the above
Answer» A. magnetic screening
70.

Standard resistor is made from

A. platinum
B. maganin
C. silver
D. nichrome
Answer» B. maganin
71.

Commonly used standard capacitor is

A. spherical type
B. concentric cylindrical type
C. electrostatic type
D. multilayer parallel plate type
Answer» B. concentric cylindrical type
72.

The most commonly used null deflector in a power frequency ac bridge is a

A. vibration galvanometer
B. d\arsanval galvanometer
C. ballistic galvanometer
D. tachometer
Answer» A. vibration galvanometer
73.

Loss of charge method is used to measure:

A. low r
B. high r
C. low l
D. high l
Answer» B. high r
74.

Megger is an instrument used for the measurement of:

A. high resistance and insulation resistance
B. medium resistance
C. low resistance
D. leakage current
Answer» A. high resistance and insulation resistance
75.

Anderson bridge is used to measure of:

A. inductance
B. capacitance
C. time period
D. resistance and capacitance
Answer» A. inductance
76.

In an electro dynamometer type of wattmeter

A. the current coil is made fixed
B. the pressure coil is fixed
C. any of the two coils current coil or pressure coil can be made fixed.
D. both the coils should be movable.
Answer» A. the current coil is made fixed
77.

In electro dynamometer type of wattmeter current coils designed for carrying heavy currents use stranded wires or laminated conductors :

A. to reduce iron losses
B. to reduce hysteresis losses
C. to reduce eddy current losses in the conductors
D. all of the above.
Answer» C. to reduce eddy current losses in the conductors
78.

In an electro dynamometer type of wattmeter , the inductance of the pressure coil circuit produces error :

A. which is constant irrespective of the power factor of the load
B. which is higher at low power factors
C. which is lower at low power factors
D. none of the above.
Answer» B. which is higher at low power factors
79.

The power in 3ph 4 wire circuit can be measured by using:

A. five watt meters
B. four watt meters
C. three watt meters
D. 1 watt meter.
Answer» C. three watt meters
80.

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

A. almost zero
B. low
C. high
D. none of the above
Answer» C. high
81.

A dynamometer wattmeter can be used for

A. both d.c. and a.c.
B. d.c. only
C. a.c. only
D. any of the above
Answer» A. both d.c. and a.c.
82.

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

A. load impedance is high
B. load impedance is low
C. supply voltage is low
D. none of the above
Answer» A. load impedance is high
83.

In a low power factor wattmeter the pressure coil is connected

A. to the supply side of the current coil
B. to the load side of the current coil
C. in any of the two meters at connection
D. none of the above
Answer» B. to the load side of the current coil
84.

In a low power factor wattmeter the compensating coil is connected

A. in series with current coil
B. in parallel with current coil
C. in series with pressure coil
D. in parallel with pressure coil
Answer» C. in series with pressure coil
85.

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

A.
B. 60°
C. 90°
D. 120°
Answer» D. 120°
86.

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

A. one voltmeter and one ammeter
B. one voltmeter, one ammetqr and one wattmeter
C. one voltmeter, one ammeter and one energy meter
D. any of the above
Answer» B. one voltmeter, one ammetqr and one wattmeter
87.

The power of a n-phase circuit can be measured by using a minimum of

A. (n - 1) wattmeter elements
B. n wattmeter elements
C. (n + 1) wattmeter elements
D. 2n wattmeter elements
Answer» A. (n - 1) wattmeter elements
88.

A Dynamometer type wattmeter responds to the:

A. average value of the active power
B. average value of the reactive power
C. peak value of the active power
D. peak value of the reactive power
Answer» A. average value of the active power
89.

The power measurement in a balanced 3-phase circuit can be done by:

A. one wattmeter method
B. two wattmeter method
C. three wattmeter method
D. any of the above method
Answer» D. any of the above method
90.

The braking torque provided by a permanent magnet in a single phase energy meter is proportional to the

A. square of the flux of the permanent magnet
B. speed of the meter
C. distance of the permanent magnet from the centre of the revolving disc
D. all of the above.
Answer» D. all of the above.
91.

Which of the following is integrating instruments?

A. power factor meter
B. energy meter
C. voltmeter
D. ammeter
Answer» B. energy meter
92.

The phenomenon of creeping occurs in

A. voltmeter
B. ammeter
C. wattmeter
D. watt-hour meter
Answer» D. watt-hour meter
93.

Hole s are drilled on the opposite sides of the spindle of an energy meter to avoid

A. balance of the disc
B. dissipate heat generated due to eddy currents
C. avoid creep on load
D. increase the deflection torque
Answer» C. avoid creep on load
94.

The pressure coil of an induction type energy meter is

A. highly inductive
B. highly resistive
C. purely inductive
D. purely resistive
Answer» A. highly inductive
95.

Which type of damping is used in Induction type energy meter?

A. air friction
B. fluid friction
C. gravity
D. eddycurrent
Answer» D. eddycurrent
96.

In an Induction type energy meter, maximum torque is obtained when the parameter of the rotating disc are

A. r=0
B. x=0
C. r=x
D. none of the above
Answer» B. x=0
97.

An Induction meter meter can handle current upto

A. 10a
B. 30a
C. 200a
D. 100a
Answer» D. 100a
98.

In an induction type energy meter, compensation for static friction is provided by

A. drilling holes in the disc
B. lag circuits
C. shading bands
D. none of the above
Answer» C. shading bands
99.

Which of the following statements is wrong

A. there is control spring
B. there is a brake magnet
C. creeping error is present
D. disc revolves continuously
Answer» A. there is control spring
100.

Which of the following is an essential part of a induction type of meter ?

A. an operating torque system
B. a braking device
C. revolution registering device
D. all of the above
Answer» D. all of the above
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