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Impedance calculation

  1. Nov 17, 2011 #1
    A 400 Ohm resistor is connected in series with an inductor of reactance 300 Ohm and a capacitor C, and a 50 V voltage is applied to the circuit.

    Find impedance.
    Is it possible to calculate it? Am I missing something or I would need Xc or I to do that? Thank you for a hint.
     
  2. jcsd
  3. Nov 17, 2011 #2

    gneill

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    Staff: Mentor

    You would need to know Xc or something else about the behavior of the circuit, such as the current, or whether the circuit was being driven at its natural frequency (resonance).
     
  4. Nov 17, 2011 #3
    you need to know the value of the capacitance and you need to know the inductive reactance (300Ω )and the capacitative reactance Xc
     
  5. Nov 17, 2011 #4
    Great thanks. One more question. I forgot to mention the Vs is at 0 degrees angle. Does it change anything?
    Becouse Vs=sqrt(Vr^2+(Vl-Vc)^2), so I am thinking that in order to have Vs<0 angle , terms Vl-Vc must be zero. So that means the Xc=Xl= 200 Ohm. Am I right about that? Thank you
     
  6. Nov 17, 2011 #5

    gneill

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    Staff: Mentor

    The angle of Vs is not diagnostic unless it's referred to the current angle. That is, you can draw conclusions about the total reactance of the circuit if you know what phase angle the current has with respect to the voltage.
     
  7. Nov 17, 2011 #6
    Ok, Thank you. I appreciate your help
     
  8. Nov 17, 2011 #7
    Usually the current is taken to be the reference direction because V and I are in phase for resistance. I would interpret V is at 0degrees to mean that V is in phase with I.
    This means that Xc and Xl are equal and the circuit is at resonance.
    It means that the impedance is just the resistance = 400ohms
     
  9. Nov 17, 2011 #8
    Thank you technician.
     
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