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Electronics Engineering QUESTION #11730
Question 1
A power analyser measures: $V_{rms} = 230\,\text{V}$, $I_{rms} = 10\,\text{A}$, $P = 1840\,\text{W}$. The power factor and reactive power $Q$ are:
  • $\text{PF} = 0.80$; $Q = 1380\,\text{VAR}$✔️
  • $\text{PF} = 0.85$; $Q = 1200\,\text{VAR}$
  • $\text{PF} = 1.0$; $Q = 0\,\text{VAR}$
  • $\text{PF} = 0.90$; $Q = 1000\,\text{VAR}$
Correct Answer Explanation
$S = V_{rms} \times I_{rms} = 230 \times 10 = 2300\,\text{VA}$. $\text{PF} = \dfrac{P}{S} = \dfrac{1840}{2300} = \mathbf{0.80}$. $Q = \sqrt{S^2 - P^2} = \sqrt{2300^2 - 1840^2} = \sqrt{5290000 - 3385600} = \sqrt{1904400} \approx \mathbf{1380\,\text{VAR}}$.