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ECE :: Measurements and Instrumentation

  1. Which of the following statement is correct for two wattmeters method of power measurement in 3 phase circuit?

  2. A.
    Power can be measured by this method only for star connected loads
    B.
    When two wattmeters have equal readings power factor is 0.5.
    C.
    When power factor is 1, one of the wattmeters readings is zero
    D.
    When the two wattmeter read equal and opposite, p.f. is zero.

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  3. In a thermocouple temperature transducer, the output voltage is usually measured by

  4. A.
    high resistance ammeter
    B.
    high resistance voltmeter
    C.
    high resistance milli-voltmeter
    D.
    none of the above

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  5. A moving iron instrument gives correct reading when used at

  6. A.
    low frequencies
    B.
    high frequencies
    C.
    only one frequency
    D.
    all frequencies upto a certain value

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  7. Induction wattmeter can be used in

  8. A.
    ac circuit only
    B.
    dc circuit only
    C.
    both ac and dc circuit
    D.
    ac 3 phase only

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  9. A dynamometer wattmeter is connected in ac circuit. The measured power is

  10. A.
    rms power
    B.
    average power
    C.
    peak power
    D.
    instantaneous power

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  11. Loss of charge method is suitable for medium resistances.

  12. A.
    True
    B.
    False

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  13. In two wattmeter method of 3 phase power measurement, when does one wattmeter read negative

  14. A.
    when power factor is less than 0.5 lagging
    B.
    when power factor is greater than 0.5 lagging
    C.
    when power factor is less than 0.5
    D.
    when power factor is unity

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  15. 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

  16. A.
    1, 2, 3, 4
    B.
    2 and 3
    C.
    1, 2, 4
    D.
    1 and 4

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  17. In figure the bridge is balanced when Z4 is

  18. A.
    120∠70°
    B.
    187.5∠ - 10°
    C.
    187.5∠ - 70°
    D.
    333.3∠ - 70°

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