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    14.素養(4)
1 如圖所示RLC 並聯電路，電源電壓v(t)＝100√2 sin(1000t)V，若I1 的電流大小為10A，IC 的電流大小為8A，則電路的功率因數為何？ 109
A 0.5
B 0.707
C 0.886
D 1
  

V=100∠0°

I12 = IC2 + IR2

IR = 6∠0° A

I1 = 6 + j8 A

XL ＝ 1000×50m ＝ 50Ω

IL = 100∠0°50∠90° = 2∠-90° = -2j

IT = 6 + j8 - j2 = 6 + j6 = 6√2∠45° A

P.F. = cosθ = cos 45° (超前) = 0.707 (超前)