GATE 2017 EE – Question 33
The following measurements are obtained on a single phase load: V = 220 V $\pm$ 1 %, I = 5.0 A $\pm$ 1% and W = 555 W $\pm$ 2 %. If the power factor is calculated using these measurements, the worst case error in the calculated power factor in percent is ________. (Give answer up to one decimal place.)
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Correct answer: 4 to 4.1
Explanation
The power factor is $\cos\phi = \frac{W}{VI}$. In the worst case the errors in the three measurements add up in the same direction, so the percentage error is $2 + 1 + 1 = 4\%$.