Impedance solution

Discussion in 'Homework Help' started by cisseywolf1, Feb 22, 2007.

  1. cisseywolf1

    Thread Starter New Member

    Feb 22, 2007
    2
    0
    Well this is my first time on a sight like this, so all please have patience. Here is my question.

    Find the impedence in a series RL circuit with R=50 ohms and L=470 microHenries at a frequency of 10kHz. If some one figures this out would you please put it in terms I can understand.

    I just started this class and I am having a very hard time. Fresh out of high school 32 yrs ago. I am now in college for the first time.
     
  2. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Hi,

    You should have a look in the tutorial at Volume II - Chapter 3.3 here at All About Circuits. Work through the tutorial and if you have any questions feel free to post them up.

    As a side point, be sure to check out the whole on-line e-book to help you with the rest of your studies.

    Dave
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    In a series RL circuit you can add the impedances of the components. The impedance of a resistor is just its resistance and it is not frequency dependent. Ahhh but the impedance of an inductor depends on the frequency. It is
    Code ( (Unknown Language)):
    1.  
    2. j*w*L
    3. where j is the imaginary unit aka sqrt(-1)
    4. w is 2*pi*frequency
    5. L is the inductance in henries
    6.  
    The result will be a complex number = R + j*2*pi*f*L
    From this complex number you can calculate the magnitude using the pythagorean theorem and you can compute the angle as the
    arctan((2*pi*f*L)/R)

    c'est facile! n'est pas?
     
  4. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    It can also be as simple as:

    inductive reactance = XL = 2*pi*F*L

    impedance = Z = sqrt(XL^2 + R^2)
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    As I said you can compute the magnitude of the complex impedance with the pythagorean theorem.
     
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