GATE 2021 IN – Question 26
A 300 V, 5 A low-power-factor wattmeter has full-scale power 300 W. For loads on 300 V AC mains, the maximum power factor permitted at its rated current is ______ (one decimal place).
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Correct answer: 0.2 to 0.2
Explanation
At 300 V and 5 A the apparent power is 1500 VA. A 300-W full-scale wattmeter can accommodate PF=P/(VI)=300/1500=**0.2** at those rated voltage/current values. Higher PF would exceed its watt scale.