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A coil of inductive reactance 3 1 Ω has a resistance of 8 Ω . It is placed in series with a condenser of capacitive reactance 2 5 Ω . The combination is connected to an ac source of 110 V . The power factor of the circuit is

Options

  1. A0 .33
  2. B0 .56
  3. C0 .64
  4. D0 .80

Correct answer

D. 0 .80

Step-by-step solution

X L = 3 1 Ω , X C = 2 5 Ω , R = 8 Ω Impedance of series L C R is Z = R 2 + X L - X C 2 = 8 2 + 3 1 - 2 5 2 = 6 4 + 3 6 = 1 0 Ω Power factor, cos ϕ = R Z = 8 1 0 = 0.8

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