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Capacitor and inductor reactance

Discussion in 'Electronics Homework Help' started by Zeeman2000, Mar 2, 2015.

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  1. Zeeman2000

    Zeeman2000

    6
    1
    Mar 2, 2015
    Hello everyone,

    I am currently working through a self study book on electronics. I have starting a chapter which is an introduction to Alternating Current. The chapter discusses capacitor and inductor reactance using the following formulas:

    XL = 2pifL
    XC = 1/2pifC

    At the end of the chapter there is a self test which gives a value of a capacitor reactance and the value of a capacitor or inductor and asks to find the frequecy necessary to cause reactance.

    The equation for this was not dicussed im the chapter. Can someone explain the equation needed to find the answer?

    I tried the equation in reverse which worked for:

    100Hz
    10H



    6.28 * 100 * 10 = 6280 ohms


    6280 / 10 / 6.28 = 100Hz


    In the self test the values are:



    L = 50 μH, XL = 320 ohms, f =


    320 / 50 / 6.28 = 1.019108280254777


    Book answer was 1.02kHz


    Not sure how they are getting this answer. Any help much appreciatted.
     
  2. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    Units in the formula are Ohm, Hertz, and Henry. 50 μH = 0.000050 H.
     
  3. Zeeman2000

    Zeeman2000

    6
    1
    Mar 2, 2015
    Yes, 50 μH = 0.000050 H

    Turns out the question in the book was wrong. I have since checked the errata and it should have read 50mH not 50μH

    As even using 0.000050 H gave and answer in MHz
     
  4. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Yep, at 50mH the answer in the book is right.

    Bob
     
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