Which of the following are needed both for protection and metering? Wattmeters I

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Question
Which of the following are needed both for protection and metering?
Options
A. Wattmeters
B. Instrument transformers
C. Energy meters
D. Power factor meters

Correct Answer

Instrument transformers

Explanation

Instrument transformers are used to measure high currents and voltages. They also feed the relays for protection.

Measurements and Instrumentation problems

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1. The coil of a moving coil meter has 100 turns, is 40 mm long and 30 mm wide. The control torque is 240 x 10^-6 N-m on full scale. If B = 1 Wb/m², range of meter is
Options
A. 1 mA
B. 2 mA
C. 3 mA
D. 4 mA

2. Which of the following measurements using a dc potentiometer do not require standardisation of potentiometer?
Options
A. Measurement of unknown voltage
B. Measurement of resistance
C. Measurement of unknown current
D. Calibration of voltmeter

3. Wave A = 100 sin ?t and wave B = 100 cos ?t. Then
Options
A. rms values of the two waves are equal
B. rms values of A is more than that of B
C. rms values of A is less than that of B
D. rms values of the two waves may or may not be equal

4. The synthesis of minimum function was suggested by
Options
A. O'Brune
B. R. Richards
C. Bott and Duffin
D. none of the above

5. In an ac circuit, the maximum and minimum values of power factor can be
Options
A. 2 and 0
B. 1 and 0
C. 0 and -1
D. 1 and -1

6. Figure shows an RC potentiometer to measure ac voltage. It is desired that V₀/V_i should be independent of frequency. The value of C should be
Options
A. 10 ?F
B. 11 ?F
C. 0.1 ?F
D. 0.09 ?F

7. Two resistors R₁ = 36 ? � 5% and R₂ = 75 ? � 5% are connected in series. The total resistance is
Options
A. 111 � 0 ?
B. 111 � 2.778 ?
C. 111 � 5.55 ?
D. 111 � 7.23 ?

8. The speed transducer using a drag cup rotor has the main advantage of
Options
A. very high accuracy
B. low energy requirement
C. cheap construction
D. all of the above

9. A digital voltmeter has a read out range from 0 to 999 counts. If the full scale reading is 9.999 V, the resolution is
Options
A. 1 V
B. 0.01 V
C. 1 mV
D. 1 ?V

10. It is required to measure angular position. Out of the transducers
1. Circular potentiometer
2. LVDT
3. E pick up
4. Synchro
The proper devices are
Options
A. 1, 2, 3, 4
B. 2 and 3
C. 1, 2, 4
D. 1 and 4

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