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Alternating Current: Cant understand the question

  1. Feb 8, 2012 #1
    Alternating Current: Cant understand the question!!...

    Hi guys...

    I was trying this question out (from alternating current) but i'm not sure whether i should do what the solution book says or listen to what my course teacher said (This is not homework, im just not clear about a line in this question...) Here goes:


    'A resistive element of 30 ohms is connected in series with an inductance coil the self inductanceof which is 50 millihenrys and the ohmic resistance of which is 4.5 ohms. A voltage v=100cos377t volts is connected to the series branch........'


    ok so here are my questions: That ohmic resistance which is mentioned, is that the XL? My teacher said it is :S... If it is then how? because XL= wL and that gives a different value..

    And if that ohmic resistance is NOT XL, then should we just add that with the 30 ohms of the resistive element? And why is an ohmic resistance of an inductor mentioned anyways? Do all inductors have a separate ohmic resistance besides having an inductive reactance??

    Im really looking forward to the reply because i've got a quiz tomorrow...

    Thanks alot in advance
     
  2. jcsd
  3. Feb 8, 2012 #2

    vk6kro

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    Science Advisor

    Re: Alternating Current: Cant understand the question!!...

    All coils have some resistance as well as inductance because they are just wound with wire which has resistance.

    In this case, the coil has 4.5 ohms of resistance and 50 mH of inductance. The reactance of the inductive component is XL or (2 * π * F * L). These are regarded as being in series although the resistance occurs along the whole length of the wire.

    It also has 30 ohms in series with it.
     
  4. Feb 8, 2012 #3
    Re: Alternating Current: Cant understand the question!!...

    ahh i get it now...so it seems the solution book is right with this question at least..anyways thanks again:)
     
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