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  • Question
  • A 2 kΩ resistor is in series with a 0.015 µF capacitor across a 15 kHz ac source. What is the magnitude of the total impedance and the phase angle?


  • Options
  • A. 73.4 Ω and ? = ?19.5°
  • B. 707 Ω and ? = ?19.5°
  • C. 2121 Ω and ? = ?19.5°
  • D. 734 Ω and ? = ?38.9°

  • Correct Answer
  • 2121 Ω and ? = ?19.5° 

    Explanation
    Xc = 1/2?fC = 707 ?

    Z = R - jXc = 2000 - j(707)

    |z| = sqrt(R*R + Xc*Xc) = 2121 ?

    Phase angle = arctangent(Xc/R) = 19.5°


    RC Circuits problems


    Search Results


    • 1. A capacitor with 150 Ω of capacitive reactance is across an ac source. The impedance, expressed in polar form, is

    • Options
    • A. Z = 150
    • B. Z = 150∠90°Ω
    • C. Z = 150 ∠?90°Ω
    • D. Z = 150∠180°Ω
    • Discuss
    • 2. What is the value of the hypotenuse of a right triangle whose sides are 12 and 18?

    • Options
    • A. 4.24
    • B. 3.46
    • C. 2.16
    • D. 21.63
    • Discuss
    • 3. In a series RC circuit, 12 V(rms) is measured across the resistor and 15 V(rms) is measured across the capacitor. The rms source voltage is

    • Options
    • A. 3 V
    • B. 27 V
    • C. 19.2 V
    • D. 1.9 V
    • Discuss
    • 4. A 470 Ω resistor and a 0.2 µF capacitor are in parallel across a 2.5 kHz ac source. The admittance, Y, in rectangular form, is

    • Options
    • A. 212 Ω
    • B. 2.12 mS + j3.14 mS
    • C. 3.14 mS + j2.12 mS
    • D. 318.3 Ω
    • Discuss
    • 5. When the frequency of the source voltage decreases, the impedance of a parallel RC circuit

    • Options
    • A. increases
    • B. decreases
    • C. does not change
    • D. decreases to zero
    • Discuss
    • 6. In a series RC circuit, when the frequency and the resistance are halved, the impedance

    • Options
    • A. doubles
    • B. is halved
    • C. is reduced to one-fourth
    • D. cannot be determined without values
    • Discuss
    • 7. When the frequency of the voltage applied to a series RC circuit is increased, the phase angle

    • Options
    • A. increases
    • B. decreases
    • C. remains the same
    • D. becomes erratic
    • Discuss
    • 8. A 120 Ω resistor is in parallel with a capacitor with a capacitive reactance of 40 Ω. Both components are across a 12 V ac source. What is the magnitude of the total impedance?

    • Options
    • A. 37.9 Ω
    • B. 3.7 Ω
    • C. 14,400 Ω
    • D. 4,800 Ω
    • Discuss
    • 9. The voltages in Problem 4 are measured at a certain frequency. To make the capacitor voltage greater than the resistor voltage, the frequency

    • Options
    • A. must be increased
    • B. must be decreased
    • C. is held constant
    • D. has no effect
    • Discuss
    • 10. A certain series resonant circuit has a bandwidth of 2 kHz. If the existing coil is replaced with one having a higher value of Q, the bandwidth will

    • Options
    • A. increase
    • B. remain the same
    • C. decrease
    • D. be less selective
    • Discuss


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