Ammeters And Voltmeters Theory - 4 - MCQs with answers

Ammeters And Voltmeters Theory - 4 - MCQs with answers

Q1. 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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Q2. Electrodynamic instruments can be used as

A. Ammeter
B. Voltmeter
C. Wattmeter
D. All of these

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Q3. The equivalent inductance of fixed coil and moving coil of electrodynamic instrument is given by

A. L₁ + L₂ + 2M

B. L₁ + L₂ - 2M

C. L₁ + L₂ + M

D. L₁ + L₂ - M

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Q4. The scale of electrodynamic instrument when it is used as ammeter and when it is used as voltmeter is

A. Uniform, uniform
B. Crowded near zero, crowded near zero
C. Cramped near zero, cramped in the middle
D. Uniform, cramped near zero

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Q5. In an electrodynamic instrument, the number of control springs present is/are

A. Two
B. One
C. Four
D. Zero

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Q6. A electrodynamic ammeter has current flowing through it of 20 A and torsional constant of controlling spring of 10^-6 N-m/degree. If the mutual inductance changes uniformly at the rate of 0.0025 μH/degree, then its angular deflection for full scale is

A. 43.68 degree
B. 57.29 degree
C. 68.32 degree
D. 69.69 degree

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Q7. For a dynamometer wattmeter, the variation of inductance with angular position of moving system is 0.06 mH/radian and spring constant is 10 X 10^-6 N-m/radian. The current flowing in the instrument is 8 A. If the full scale deflection is 76 degree, then the current required in the voltage coil at full scale on d.c. circuit is

A. 27.6 μA
B. 29.89 μA
C. 35.3 μA
D. 37.28 μA

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Q8. The deflection angle in hot wire instruments is

A. Directly proportional to the current
B. Directly proportional to the square of current
C. Inversely proportional to the current
D. Inversely proportional to the square of current

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Q9. Hot-wire instruments are suitable for

A. Ac work only
B. Dc work only
C. Both ac and dc work
D. None of these

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Q10. The current sensitive instruments are

A. PMMC
B. Hot wire instruments
C. Electrostatic instruments
D. Both (a) and (b)

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