1) In a gravity controlled type indicating instrument, the current flowing through the circuit is
a. Directly proportional to the cosine of angle of deflection
b. Directly proportional to the sine of angle of deflection
c. Directly proportional to the tan of the angle of deflection
d. Directly proportional to the angle of deflection
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Answer
Explanation
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ANSWER: Directly proportional to the sine of angle of deflection
Explanation:
No explanation is available for this question!
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2) The scales of gravity controlled instruments are
a. Uniform
b. Non-uniform and cramped or crowded at the middle
c. Non-uniform and cramped or crowded at their lower ends
d. Non-uniform and cramped or crowded in the first half
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Answer
Explanation
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ANSWER: Non-uniform and cramped or crowded at their lower ends
Explanation:
No explanation is available for this question!
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3) The gravity controlled instruments has to be kept
a. Vertical
b. Horizontal
c. Inclined at 45 degree
d. Inclined at 75 degree
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4) A deflection of 90 degree is produced when a current of 10 A flows through the circuit and the torque of the ammeter vary as the square of the current through it. If a current of 8 A flows through it, then the deflection obtained when the instrument is spring controlled and when the instrument is gravity controlled are
a. 39.79 degree, 57.6 degree
b. 47.55 degree, 35.67 degree
c. 57.6 degree, 39.79 degree
d. 35.67 degree, 47.55 degree
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5) Damping torque is the torque which acts on
a. Stationary system of the instrument
b. Moving system of the instrument only when it is stationary
c. Moving system of the instrument only when it is moving
d. Stationary system of the instrument only when the moving system is moving
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Answer
Explanation
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ANSWER: Moving system of the instrument only when it is moving
Explanation:
No explanation is available for this question!
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6) If the degree of damping of an instrument should be adjusted to a value which is sufficient to enable the pointer to rise quickly to its deflected position without overshooting is called as
a. Overdamped
b. Dead beat
c. Underdamped
d. None of these
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7) Due to overdamping, the instrument will become
a. Slow
b. Lethargic
c. Fast
d. Both (a) and (b)
e. None of these
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8) The damping force in an instrument can be produced by air friction, eddy currents and fluid friction. Which among the three is most efficient?
a. Air friction
b. Eddy current
c. Fluid friction
d. All are equally efficient
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9) The time response of an indicating instrument is determined from the
a. Damping torque
b. Controlling torque
c. Deflecting torque
d. All of these
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10) The instrument which can be used only with the d.c. supply is
a. PMMC instrument
b. Electrodynamometer instrument
c. Hot-wire instrument
d. Split phase induction type instrument
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11) The instrument which can be used only with the a.c. supply is / are
a. Induction type
b. Electrostatic type
c. Electrodynamometer type
d. All of these
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12) In a hot wire ammeter the current flowing through the resistance of 10Ω is given by
I = 3 + 2sin300t A
The measured value of current will be
a. 2.98 A
b. 3.31 A
c. 3.62 A
d. 4.01 A
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13) In a hot wire instrument, readings are
a. Dependent on frequency
b. Dependent on waveform
c. Dependent on both frequency and waveform
d. Independent of both frequency and waveform
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14) To convert a 2 mA meter with internal resistance of 120 ohm into an ammeter of range 0 – 200 mA, the value of shunt resistance required is
a. 1.121 ohm
b. 1.212 ohm
c. 1.312 ohm
d. 1.414 ohm
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15) If a moving iron instrument is to be used as ammeter then the coil has
a. Fewer number of turns of thin wire
b. Fewer number of turns of thick wire
c. Larger number of turns of thin wire
d. Larger number of turns of thick wire
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16) If the direction of current through the coil is upward, then the iron disc will be magnetized in such a way that it is
a. Pushed outwards
b. Pushed upwards
c. Pushed downwards
d. Pulled inwards
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17) A spring controlled moving iron voltmeter with full scale deflection of 150 V draws a current of 2 mA. What will be the meter reading if it draws a current of 1 mA?
a. 25.5 V
b. 27.5 V
c. 35.5 V
d. 37.5 V
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18) A repulsion type moving iron instrument when used with a.c. circuits, the deflecting torque is
a. Directly proportional to the rms current
b. Directly proportional to the square of rms current
c. Directly proportional to the peak current
d. Directly proportional to the square of the peak current
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Answer
Explanation
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ANSWER: Directly proportional to the square of rms current
Explanation:
No explanation is available for this question!
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19) What will a moving iron ammeter read if a rectangular waveform current with peak value of 120 mA is passed through it?
a. 120 mA
b. 84.8 mA
c. 169.7 mA
d. 60 mA
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20) A moving iron instrument is used as an ammeter. Its range can be extended by using
a. Suitable shunt across its terminal
b. A high non-inductive resistance
c. Both (a) and (b)
d. None of these
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21) For a moving iron ammeter, the change of inductance is 3 μH/degree and its spring constant is 4 X 10-7 N-m/degree. If the maximum deflection of the pointer is 90 degree, then the corresponding current in the coil be
a. 3.89 A
b. 4.05 A
c. 4.89 A
d. 5 A
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22) For extending the range of 0-150 V to 0-500 V in a 10000 Ω/V meter, the value of series resistance required is equal to
a. 3 M Ω
b. 3.5 M Ω
c. 4 M Ω
d. 4.5 M Ω
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23) A current of 2 + 3sinωt A is passed through a moving iron instrument and through a PMMC meter respectively. The readings of the two meters are
a. 2 A, 2A
b. 2 A, 2.9 A
c. 2.9 A, 2.9 A
d. 2.9 A, 2 A
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24) In a permanent magnet moving coil instrument, the deflecting torque is
a. Directly proportional to both number of turns and flux density
b. Directly proportional to the number of turns and inversely proportional to the flux density
c. Inversely proportional to the number of turns and directly proportional to the flux density
d. Inversely proportional to both number of turns and flux density
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Answer
Explanation
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ANSWER: Directly proportional to both number of turns and flux density
Explanation:
No explanation is available for this question!
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25) The coil diameter and length of a PMMC instrument is 1.2 cm and 1.8 cm respectively. The magnetic flux density in air is 0.1 T and the number of turns is 100. If the current of 1.5 mA is flowing through it then the torque produced on the coil is
a. 2.58 X 10-6 N-m
b. 2.92 X 10-6 N-m
c. 3.24 X 10-6 N-m
d. 3.92 X 10-6 N-m
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26) The scale of PMMC type instruments is
a. Uniform
b. Non-uniform
c. Cramped at the lower ends
d. Crowded in the middle
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27) An ac voltage source of 2sint V is connected in series with a dc voltage source of 5 V. If a PMMC instrument is connected in parallel to this combination then the reading of meter will be equal to
a. 7 V
b. 5 V
c. 5.2 V
d. 25 V
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28) The deflecting torque in a moving coil instrument is
a. Directly proportional to the current flowing through it
b. Inversely proportional to the current flowing through it
c. Inversely proportional to the square of current flowing through it
d. Directly proportional to the square of current flowing through it
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Answer
Explanation
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ANSWER: Directly proportional to the square of current flowing through it
Explanation:
No explanation is available for this question!
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29) When an ac signal is applied across the permanent magnet moving coil voltmeter, then the pointer will
a. Not deflect
b. Oscillate around zero volt
c. Deflect to its maximum
d. Oscillate from minimum to maximum value
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30) If the control spring of PMMC instrument is replaced by a another spring whose spring constant is higher than the previous one, then the damping ratio and natural frequency
a. Increases, decreases
b. Increases, increases
c. Decreases, decreases
d. Decreases, increases
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31) A PMMC instrument can be used as ammeter and as voltmeter with the help of
a. A low resistance shunt, a low series resistance
b. A low resistance shunt, a high series resistance
c. A high series resistance, a low resistance shunt
d. A low series resistance, a high shunt resistance
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Answer
Explanation
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ANSWER: A low resistance shunt, a high series resistance
Explanation:
No explanation is available for this question!
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32) In a PMMC instrument, if the control springs are eliminated the instrument can be used for measuring the quantity of electricity passed through the coil. This method is used for
a. Ammeter
b. Voltmeter
c. Fluxmeter
d. Ballistic galvanometer
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33) If the control springs of PMMC instrument is made up of large moment of inertia, then it can be used as
a. Ammeter
b. Fluxmeter
c. Ballistic galvanometer
d. Wattmeter
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34) The ratio of maximum current (with shunt) to the full scale deflection current (without current) in a permanent magnet moving coil instrument is known as
a. Sensitivity
b. Multiplying factor
c. Multiplying power
d. Both (b) and (c)
e. None of these
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35) The multiplying factor of a PMMC used as ammeter is
a. Directly proportional to the shunt resistance
b. Inversely proportional to the shunt resistance
c. Inversely proportional to the series resistance
d. Directly proportional to the series resistance
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Answer
Explanation
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ANSWER: Inversely proportional to the shunt resistance
Explanation:
No explanation is available for this question!
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36) The voltage multiplication factor of a PMMC instrument is
a. Directly proportional to the required series resistance
b. Directly proportional to the shunt resistance
c. Inversely proportional to the shunt resistance
d. Directly proportional to the required series resistance
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Answer
Explanation
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ANSWER: Directly proportional to the required series resistance
Explanation:
No explanation is available for this question!
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37) A moving coil ammeter requires a potential difference of 0.4V across it for full scale deflection. It has fixed shunt resistance of 0.01 ohm with a coil circuit resistance of R = 1kohm. The value of shunt required to give full scale deflection when the total current is 10A is equal to
a. 0.02 ohm
b. 0.04 ohm
c. 0.05 ohm
d. 0.06 ohm
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38) A PMMC instrument gives full scale deflection at 40 mV potential difference and 8 mA current. What will be the required shunt resistance when it is used as ammeter of range 0 – 10 A?
a. 0.002 ohm
b. 0.003 ohm
c. 0.004 ohm
d. 0.005 ohm
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39) A permanent magnet moving coil gives full scale deflection at 40 mV potential difference and 8 mA current. What will be the required series resistance when it is used as voltmeter of range 0 – 200 V?
a. 19556 ohm
b. 20163 ohm
c. 23884 ohm
d. 24995 ohm
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40) In electrodynamic instruments, the operating field is produced by
a. Permanent magnet
b. Fixed coil
c. Moving coil
d. All of these
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