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E5B07

ELECTRICAL PRINCIPLES · Time constants and phase relationships: RL and RC time constants; phase angle in reactive circuits and components; admittance and susceptance

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What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 500 ohms, R is 1 kilohm, and XL is 250 ohms?

  1. A68.2 degrees with the voltage leading the current
  2. B14.0 degrees with the voltage leading the current
  3. C14.0 degrees with the voltage lagging the current
  4. D68.2 degrees with the voltage lagging the current
Why In a series RLC circuit the reactances subtract: X = XL - XC = 250 - 500 = -250 ohms, so the net reactance is capacitive. The phase angle is arctan(X/R) = arctan(250/1000) = 14.0 degrees. Because the circuit is net capacitive, the current leads the voltage, which is the same as saying the voltage lags the current.
Watch out The 14.0 degrees with voltage leading choice has the right magnitude but the wrong sign; voltage leads only when XL is larger than XC (net inductive). The 68.2 degree answers come from flipping the ratio and taking arctan(1000/250).
ELI the ICE man: with C dominant (ICE), current leads. Angle = arctan(net X / R), here arctan(250/1000) = 14 degrees.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
← E5B06 All of E5B E5B08 →

The rest of E5B

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  4. E5B04 What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors, all i…
  5. E5B05 What is the effect on the magnitude of pure reactance when it is converted to susceptance?
  6. E5B06 What is susceptance?
  7. E5B07 What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 500 …
  8. E5B08 What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 300 …
  9. E5B09 What is the relationship between the AC current through a capacitor and the voltage across a capacitor?
  10. E5B10 What is the relationship between the AC current through an inductor and the voltage across an inductor?
  11. E5B11 What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 25 o…
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