Measurements and Instrumentation
In 3 phase power measurement by two wattmeter method, the reading of one wattmeter is zero. The power factor of load is
Answer: B
When p.f. = 0.5, 0 = 60° and one of the wattmeters reads zero.
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A moving iron instrument gives correct reading when used at
Answer: C
If frequency changes reactance of coil changes and reading is affected.
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Assertion (A): De sauty's bridge is suitable only for pure capacitor.
Reason (R): Capacitors are mostly perfect.
Answer: C
Capacitors are mostly imperfect.
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The scale of hot wire instrument is linear.
Answer: B
Since reading is proportional to I2, the scale is non-linear.
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Two numbers are 131 ± 5 and 629 ± 3. The sum of the numbers with range of doubt is
Answer: A
The numbers can be 131 + 5, 131 - 5, 629 - 3. Therefore, the sum can be 760 ± 8.
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Assertion (A): Shunt of an ammeter has a low resistance.
Reason (R): Shunt may be connected in series or in parallel with ammeter.
Answer: C
Shunt is always connected in parallel with ammeter.
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A meter with a resistance of 100 Ω and a full scale deflection of current of 1 mA is to be converted into voltmeter of 0 - 5 V range. The multiplier resistance should be
Answer: C
.
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An LVDT is used to measure displacement. The LVDT feeds a Voltmeter of 0-5 V range through a 250 gain amplifier. For a displacement 0.5 mm the output of LVDT is 2 mV. The sensitivity of instrument is
Answer: C
Final output = 2 x 10-3 x 250 = 0.5 V.
.
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If an inductance L is connected in one arm of bridge and resistance R1, R2, R3 in other three arms
Answer: A
To balance the bridge both magnitudes and phase angles of voltages have to be balanced.
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