Ammeters And Voltmeters Theory - 2 - MCQs with answers

Ammeters And Voltmeters Theory - 2 - MCQs with answers

Q1. 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. Neither (a) nor (b)

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Q2. 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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Q3. 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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Q4. 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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Q5. 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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Q6. 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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Q7. 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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Q8. 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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Q9. 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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Q10. 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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