In a moving iron instrument, the deflecting torque is:

∝ 1 / i, where i is the current through the instrument

∝ i, where i is the current through the instrument

∝ 1 / i2, where i is the current through the instrument

∝ i2, where i is the current through the instrument

∝ 1 / i, where i is the current through the instrument

Direction: It consists of two statements, one labeled as ‘Statement (I)’ and the others as ‘Statement (II)’. You are to examine these two statements carefully and select the answer using the codes given below:Statement (I): In an ac dynamometer-type wattmeter the instantaneous value of developed deflecting torque is proportional to the product of voltage and current in the respective coils at the corresponding instant, the constant of proportionality is the same as in the case of dc use.Statement (II): The moving system of the meter is prevented by its Inertia from following the variations in the deflecting torque which takes place during each cycle, and takes up a position corresponding to the average value of the torque.

Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)

Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)

Statement (I) is true but Statement (II) is false

Statement (I) is false but Statement (II) is true

In a PMMC instrument, the final steady state deflection is:

∝ 1 / i, where i is the current through the coil

∝ i, where i is the current through the coil

∝ 1 / i, where i is the current through the coil

∝ i2, where i is the current through the coil

∝ 1 / i2, where I is the current through the coil

Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I):The simplest method of power measurement is by means of electro dynamic type wattmeters, having two fixed coils, and one moving coil.Statement (II):Either of the fixed and the moving coils can be used as the current or the voltage coils.

Statement (I) is false but Statement (II) is true

Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)

Statement (I) is true but Statement (II) is false

Statement (I) is false but Statement (II) is true

An ammeter has a current range of 0-5 A, and its internal resistance is 0.2 Ω. In order to change the range to 0-25 A, we need to add a resistance of

0.8 Ω in series with the meter

1.0 Ω in series with the meter

0.04 Ω in parallel with the meter

0.05 Ω in parallel with the meter

In an electrodynamometer wattmeter

if the full-scale power measured is 100 W, then the half-scale power will be 10 W

the fixed coils providing magnetic flux are connected across the power line

the compensated wattmeter improves its accuracy by using windings with opposite currents with respect to series windings

if the full-scale power measured is 100 W, then the half-scale power will be 10 W

it can measure a.c. power but is unsuitable for d.c. power

Match the following: Instrument type Used for P) Permanent magnet moving coil 1. DC only Q) Moving iron connected through current transformer 2. AC only R) Rectifier 3. DC and AC S) Electrodynamometer

P – 3, Q – 1, R – 2, S – 1

P – 1, Q – 2, R – 1, S – 3

P – 1, Q – 3, R – 1, S – 2

P – 1, Q – 2, R – 3, S – 3

P – 3, Q – 1, R – 2, S – 1

Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I):A permanent magnet moving coil instrument is always slightly under damped.Statement (II):The pointer of the PMMC instrument should overshoot a little beyond the steady-state position to give the accurate reading.

Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)

Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)

Statement (I) is true but Statement (II) is false

Statement (I) is false but Statement (II) is true

In a low power factor wattmeter compensating coil is connected:

In parallel with the pressure coil

In series with the current coil

In series with the pressure coil

In parallel with the pressure coil

In parallel with the current coil

Electro dynamometer type of instruments are enclosed in a casing made up of high permeability material to:

To remove electrostatic effects.

To provide mechanical strength to the coils present.

To protect against external magnetic fields.

Direction: It consists of two statements, one labelled as Statement (I) and the other as Statement (II). Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I): In instruments where spring control is used for providing controlling torque, the scale is uniform, and where gravity control is used, the scale is non-uniform.Statement (II): In instruments where controlling torque is provided by spring control, the current is proportional to the deflection, and where the controlling torque is provided by gravity control, the current is proportional to sine of the deflection.

Both statement (I) and Statement (II) are individually true and Statement (II) is not the correct explanation of Statement (I)

Both statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

Both statement (I) and Statement (II) are individually true and Statement (II) is not the correct explanation of Statement (I)

Statement (I) is true but Statement (II) is false

Statement (I) is false but Statement (II) is true

A PMMC instrument if connected directly to measure alternating current, it indicates

1/√2 of the scale value where the pointer rests

the actual value of the subject AC quantity

1/√2 of the scale value where the pointer rests

√3/2 of the scale value where the pointer rests

36 + Mcqs in Indicating Instruments in Electrical Engineering Page 1 McqOptions

1.	A current of -4 + 3√2 sin (ωt + 30°) A is passed through a centre zero PMMC meter and moving-iron meter. The two meters will read respectively
A.	-4 A and -5 A
B.	4 A and -5 A
C.	-4 A and 5 A
D.	4 A and 5 A
Answer» D. 4 A and 5 A

Discussion

2.	In a moving iron instrument, the deflecting torque is:
A.	∝ i, where i is the current through the instrument
B.	∝ 1 / i2, where i is the current through the instrument
C.	∝ i2, where i is the current through the instrument
D.	∝ 1 / i, where i is the current through the instrument
Answer» D. ∝ 1 / i, where i is the current through the instrument

Discussion

3.	A 0-1 Ampere moving iron ammeter has an internal resistance of 50 mΩ and inductance of 0.1 mH. A shunt coil is connected to extend its range to 0-10 Ampere for all operating frequencies. The time constant in milliseconds and resistance in mΩ of the shunt coil respectively are
A.	2, 5.55
B.	2, 1
C.	2.18, 0.55
D.	11.1, 2
Answer» B. 2, 1

Discussion

4.	Calculate the reading of voltmeter when 110 V 50 Hz is supplied across PMMC voltmeter having internal resistance 10 kΩ and full-scale range of 0-220 V.
A.	55 V
B.	78 V
C.	110 √2 V
D.	0 V
Answer» E.

Discussion

5.	In an ammeter, The deflecting torque is proportional to the current passing through it, and the instrument has full scale deflection of 80° for a current of 5 A. What deflection will occur for a current of 2.5 A when the instrument is spring-controlled?
A.	20°
B.	35°
C.	45°
D.	40°
Answer» E.

Discussion

6.	Direction: It consists of two statements, one labeled as ‘Statement (I)’ and the others as ‘Statement (II)’. You are to examine these two statements carefully and select the answer using the codes given below:Statement (I): In an ac dynamometer-type wattmeter the instantaneous value of developed deflecting torque is proportional to the product of voltage and current in the respective coils at the corresponding instant, the constant of proportionality is the same as in the case of dc use.Statement (II): The moving system of the meter is prevented by its Inertia from following the variations in the deflecting torque which takes place during each cycle, and takes up a position corresponding to the average value of the torque.
A.	Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B.	Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)
C.	Statement (I) is true but Statement (II) is false
D.	Statement (I) is false but Statement (II) is true
Answer» B. Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)

Discussion

7.	A periodic waveform observed across a load is represented by\(V\left( t \right) = \left\{ {\begin{array}{*{20}{c}}{1 + \sin \omega t,\;\;0 \le \omega t < 6\pi }\\{ - 1 + \sin \omega t,\;\;6\pi \le \omega t < 12\pi }\end{array}} \right.\)The measured value, using moving iron voltmeter connected across the load, is
A.	\(\sqrt {\frac{3}{2}} \)
B.	\(\sqrt {\frac{2}{3}} \)
C.	\(\frac{3}{2}\)
D.	\(\frac{2}{3}\)
Answer» B. \(\sqrt {\frac{2}{3}} \)

Discussion

8.	_______ instruments give the value of measurand in terms of instrument constant and its deflection.
A.	Integral
B.	Active
C.	Secondary
D.	Absolute
Answer» E.

Discussion

9.	Based on which principle does a Moving Coil meter work?
A.	Faraday’s Current law
B.	Faraday’s Voltage law
C.	Ohm's law
D.	Maxwell's law
Answer» C. Ohm's law

Discussion

10.	Highest flux density exists inside which of the following instruments?
A.	Electrodynamic instruments
B.	Hot wire instruments
C.	Moving iron instruments
D.	Moving coil instruments
Answer» E.

Discussion

11.	In a PMMC instrument, the final steady state deflection is:
A.	∝ i, where i is the current through the coil
B.	∝ 1 / i, where i is the current through the coil
C.	∝ i2, where i is the current through the coil
D.	∝ 1 / i2, where I is the current through the coil
Answer» B. ∝ 1 / i, where i is the current through the coil

Discussion

12.	Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I):The simplest method of power measurement is by means of electro dynamic type wattmeters, having two fixed coils, and one moving coil.Statement (II):Either of the fixed and the moving coils can be used as the current or the voltage coils.
A.	Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B.	Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
C.	Statement (I) is true but Statement (II) is false
D.	Statement (I) is false but Statement (II) is true
Answer» D. Statement (I) is false but Statement (II) is true

Discussion

13.	An ammeter has a current range of 0-5 A, and its internal resistance is 0.2 Ω. In order to change the range to 0-25 A, we need to add a resistance of
A.	0.8 Ω in series with the meter
B.	1.0 Ω in series with the meter
C.	0.04 Ω in parallel with the meter
D.	0.05 Ω in parallel with the meter
Answer» E.

Discussion

14.	Identify the instrument that does not exist:
A.	Dynamometer-type ammeter
B.	Dynamometer-type wattmeter
C.	Moving-iron voltmeter
D.	Moving-iron wattmeter
Answer» E.

Discussion

15.	In a PMMC type instrument, which type of damping is employed?
A.	Fluid friction damping
B.	Eddy current damping
C.	Air friction damping
D.	No damping
Answer» C. Air friction damping

Discussion

16.	Moving-coil permanent magnet instruments can be used for the measurement of
A.	AC and DC
B.	AC only
C.	DC only
D.	half-wave rectified DC
Answer» D. half-wave rectified DC

Discussion

17.	A moving coil of a meter has 100 turns and a length and depth of 10 mm and 20 mm respectively. It is positioned in a uniform redial flux density of 200 mT. The coil carries a current of 50 mA. The torque on the coil is
A.	200 μN – m
B.	100 μN – m
C.	1000 μN – m
D.	1 μN – m
Answer» B. 100 μN – m

Discussion

18.	In an electrodynamometer wattmeter
A.	the fixed coils providing magnetic flux are connected across the power line
B.	the compensated wattmeter improves its accuracy by using windings with opposite currents with respect to series windings
C.	if the full-scale power measured is 100 W, then the half-scale power will be 10 W
D.	it can measure a.c. power but is unsuitable for d.c. power
Answer» C. if the full-scale power measured is 100 W, then the half-scale power will be 10 W

Discussion

19.	Match the following: Instrument type Used for P) Permanent magnet moving coil 1. DC only Q) Moving iron connected through current transformer 2. AC only R) Rectifier 3. DC and AC S) Electrodynamometer
A.	P – 1, Q – 2, R – 1, S – 3
B.	P – 1, Q – 3, R – 1, S – 2
C.	P – 1, Q – 2, R – 3, S – 3
D.	P – 3, Q – 1, R – 2, S – 1
Answer» D. P – 3, Q – 1, R – 2, S – 1

Discussion

20.	If the current through a moving iron instrument is increased by 20%, what is the percentage increase in the deflection torque?
A.	40
B.	25
C.	32
D.	44
Answer» E.

Discussion

21.	AC current cannot be measured directly by _______
A.	Hot wire ammeter
B.	Moving iron ammeter
C.	Moving coil ammeter
D.	Thermocouple type ammeter
Answer» D. Thermocouple type ammeter

Discussion

22.	Current flowing in a circuit is i = (18 + 10sinωt + 7sin2ωt). A moving iron ammeter is connected in the circuit to measure this current. The reading of the meter will be approximately
A.	28 A
B.	35 A
C.	18 A
D.	20 A
Answer» E.

Discussion

23.	Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I):A permanent magnet moving coil instrument is always slightly under damped.Statement (II):The pointer of the PMMC instrument should overshoot a little beyond the steady-state position to give the accurate reading.
A.	Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B.	Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
C.	Statement (I) is true but Statement (II) is false
D.	Statement (I) is false but Statement (II) is true
Answer» B. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)

Discussion

24.	An ac voltmeter uses the circle shown below where the PMMC meter has an internal resistance of 100 Ω and requires a DC current of 1 mA for full scale deflection. Assuming the diodes to be ideal, the value of Rs to obtain full scale deflection with 100 V (ac rms) applied to the input terminal would be
A.	80 kΩ
B.	89 kΩ
C.	89.9 kΩ
D.	90 kΩ
Answer» D. 90 kΩ

Discussion

25.	A moving-coil ammeter has spring giving a control constant of 0.2 × 10-6 Nm/degree. If the deflecting torque on the instrument 24 × 10-6 Nm, find the angular deflection of the pointer.
A.	120°
B.	40°
C.	90°
D.	100°
Answer» B. 40°

Discussion

26.	Air friction damping is used in a/an _______ instrument.
A.	Hot wire
B.	Induction
C.	Moving iron
D.	Moving coil
Answer» D. Moving coil

Discussion

27.	A measuring instrument that uses gravity control for applying the controlling torque can only be used in ______ position.
A.	vertical
B.	horizontal
C.	slanting, upto 120 degrees
D.	slanting, upto 45 degrees
Answer» B. horizontal

Discussion

28.	In a low power factor wattmeter compensating coil is connected:
A.	In series with the current coil
B.	In series with the pressure coil
C.	In parallel with the pressure coil
D.	In parallel with the current coil
Answer» C. In parallel with the pressure coil

Discussion

29.	A current waveform, i(t), shown in the figure, is passed through a Permanent Magnet Moving Coil (PMMC) type ammeter. The reading of the ammeter up to two decimal places is
A.	-0.25 A
B.	-0.12 A
C.	0.37 A
D.	0.5 A
Answer» B. -0.12 A

Discussion

30.	Electro dynamometer type of instruments are enclosed in a casing made up of high permeability material to:
A.	To remove electrostatic effects.
B.	To provide mechanical strength to the coils present.
C.	To protect against external magnetic fields.
D.	Provide good damping
Answer» D. Provide good damping

Discussion

31.	In a dynamometer wattmeter, the moving coil is:
A.	current coil
B.	low power factor coil
C.	compensating coil
D.	potential coil
Answer» E.

Discussion

32.	Direction: It consists of two statements, one labelled as Statement (I) and the other as Statement (II). Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I): In instruments where spring control is used for providing controlling torque, the scale is uniform, and where gravity control is used, the scale is non-uniform.Statement (II): In instruments where controlling torque is provided by spring control, the current is proportional to the deflection, and where the controlling torque is provided by gravity control, the current is proportional to sine of the deflection.
A.	Both statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B.	Both statement (I) and Statement (II) are individually true and Statement (II) is not the correct explanation of Statement (I)
C.	Statement (I) is true but Statement (II) is false
D.	Statement (I) is false but Statement (II) is true
Answer» B. Both statement (I) and Statement (II) are individually true and Statement (II) is not the correct explanation of Statement (I)

Discussion

33.	A periodic voltage waveform observed on an oscilloscope across a load is shown. A permanent magnet moving coil (PMMC) meter connected across the same load reads
A.	4 V
B.	5 V
C.	8 V
D.	10 V
Answer» B. 5 V

Discussion

34.	A PMMC voltmeter has an available maximum voltage deflection (full scale deflection) current of 50 μA. If the meter has a range of 50 V and the coil resistance is 100 Ω, what will be the sensitivity of the voltmeter?
A.	20 kΩ/V
B.	10 kΩ/V
C.	40 kΩ/V
D.	100 kΩ/V
Answer» B. 10 kΩ/V

Discussion

35.	Following statements are given for electrodynamometer-type instruments:a) It is used for a.c. quantities onlyb) It is used for both a.c. and d.c. quantitiesc) It can be used to measure power and frequencyd) It has only one coilOut of the above statements, which are correct?
A.	and b) are correct
B.	and c) are correct
C.	and d) are correct
D.	and a) are correct
Answer» C. and d) are correct

Discussion

36.	A PMMC instrument if connected directly to measure alternating current, it indicates
A.	the actual value of the subject AC quantity
B.	zero reading
C.	1/√2 of the scale value where the pointer rests
D.	√3/2 of the scale value where the pointer rests
Answer» C. 1/√2 of the scale value where the pointer rests

Discussion

Explore topic-wise MCQs in Electrical Engineering.

A current of -4 + 3√2 sin (ωt + 30°) A is passed through a centre zero PMMC meter and moving-iron meter. The two meters will read respectively

In a moving iron instrument, the deflecting torque is:

A 0-1 Ampere moving iron ammeter has an internal resistance of 50 mΩ and inductance of 0.1 mH. A shunt coil is connected to extend its range to 0-10 Ampere for all operating frequencies. The time constant in milliseconds and resistance in mΩ of the shunt coil respectively are

Calculate the reading of voltmeter when 110 V 50 Hz is supplied across PMMC voltmeter having internal resistance 10 kΩ and full-scale range of 0-220 V.

In an ammeter, The deflecting torque is proportional to the current passing through it, and the instrument has full scale deflection of 80° for a current of 5 A. What deflection will occur for a current of 2.5 A when the instrument is spring-controlled?

_______ instruments give the value of measurand in terms of instrument constant and its deflection.

Based on which principle does a Moving Coil meter work?

Highest flux density exists inside which of the following instruments?

In a PMMC instrument, the final steady state deflection is:

An ammeter has a current range of 0-5 A, and its internal resistance is 0.2 Ω. In order to change the range to 0-25 A, we need to add a resistance of

Identify the instrument that does not exist:

In a PMMC type instrument, which type of damping is employed?

Moving-coil permanent magnet instruments can be used for the measurement of

A moving coil of a meter has 100 turns and a length and depth of 10 mm and 20 mm respectively. It is positioned in a uniform redial flux density of 200 mT. The coil carries a current of 50 mA. The torque on the coil is

In an electrodynamometer wattmeter

Match the following: Instrument type Used for P) Permanent magnet moving coil 1. DC only Q) Moving iron connected through current transformer 2. AC only R) Rectifier 3. DC and AC S) Electrodynamometer

If the current through a moving iron instrument is increased by 20%, what is the percentage increase in the deflection torque?

AC current cannot be measured directly by _______

Current flowing in a circuit is i = (18 + 10sinωt + 7sin2ωt). A moving iron ammeter is connected in the circuit to measure this current. The reading of the meter will be approximately

A moving-coil ammeter has spring giving a control constant of 0.2 × 10-6 Nm/degree. If the deflecting torque on the instrument 24 × 10-6 Nm, find the angular deflection of the pointer.

Air friction damping is used in a/an _______ instrument.

A measuring instrument that uses gravity control for applying the controlling torque can only be used in ______ position.

In a low power factor wattmeter compensating coil is connected:

A current waveform, i(t), shown in the figure, is passed through a Permanent Magnet Moving Coil (PMMC) type ammeter. The reading of the ammeter up to two decimal places is

Electro dynamometer type of instruments are enclosed in a casing made up of high permeability material to:

In a dynamometer wattmeter, the moving coil is:

A periodic voltage waveform observed on an oscilloscope across a load is shown. A permanent magnet moving coil (PMMC) meter connected across the same load reads

A PMMC voltmeter has an available maximum voltage deflection (full scale deflection) current of 50 μA. If the meter has a range of 50 V and the coil resistance is 100 Ω, what will be the sensitivity of the voltmeter?

Following statements are given for electrodynamometer-type instruments:a) It is used for a.c. quantities onlyb) It is used for both a.c. and d.c. quantitiesc) It can be used to measure power and frequencyd) It has only one coilOut of the above statements, which are correct?

A PMMC instrument if connected directly to measure alternating current, it indicates