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Multiple Choice Question (MCQ) of Measurements page-11


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101. For a good 0.5 micro-farad paper capacitor, the ohm-meter reading should

a) Go quickly to 100 ohms and remain there
b) Show low resistance momentarily and back off to a very high resistance
c) Not move at all
d) Show very high resistance first and then low

Ans: (b)

102. Which of the following error may arise in wattmeter if it is not compensated for the errors?

a) Voltage coil inductance
b) Voltage coil capacitance
c) Eddy currents
d) (a), (b) and (c)

Ans: (d)

103. Which of the following is methods is the commonest method of measuring three balanced or unbalanced power?

a) One wattmeter method
b) Two wattmeter method
c) Three wattmeter method
d) Ammeter method

Ans: (b)

104. One-Wattmeter method is used to measure

a) The power when load is balance in three phase circuit
b) The power when load is unbalanced in three phase circuit
c) (a) or (b)
d) Single phase power with balanced load

Ans: (a)

105. The reactive power can be measured with wattmeter when voltage across voltage coil is adjusted to be out of phase with the current by

a) 90°
b) 180°
c) 45°
d) 0°
e) 120°

Ans: (a)

106.The change of frequency affects the circuit parameters of wattmeter connected to measure power of three-phase AC system

a) True
b) False

Ans: (b)

107. Which of the following devices are required to measure three phase balance power?

a) One wattmeter
b) One wattmeter and one voltage transformer of 1:1 ratio
c) One wattmeter and two current transformers of 1:1 ratio
d) Either (b) or (c)

Ans: (d)

108. The total power P measured in Y star three-phase circuit is given by

a) P = 3VI cos ⁡ϕ
b) P = √I cos ⁡ϕ
c) P = √3VI cos ⁡ϕ
d) P = √2VI cos⁡ ϕ

Ans: (c)

Where V and I are the line voltage and line current respectively.

109.In the above question, the power in delta three-phase circuit is given by

a) P = 3 VI cos ⁡ϕ
b) P = √3 VI cos ⁡ϕ
c) P = √2 VI cos ⁡ϕ
d) P = √3 VI sin ⁡ϕ

Ans: (b)

110. The dynamometer wattmeter can be used to measure

a) AC power only
b) DC power only
c) AC or DC power
d) AC power of single-phase circuits

Ans: (c)


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