AC Circuit Theory

Discussion in 'Homework Help' started by ForgottenMemorie, Mar 26, 2008.

  1. ForgottenMemorie

    Thread Starter New Member

    Mar 26, 2008
    Im new i hope you can help. If i can see the process on how to solve this, i will be able to do my other questions by myself.


    A circuit consists of a resistor of 2 ohms connected in series with a pure inductance and a pure capacitance.

    The value of the inductance is 130ųH and the capacitance is 0.5ųF.

    The circuit is connected across a 1< 0° volt AC 100kHz supply.


    1. The magnitude of the current flowing in the circuit

    2. The phase angle of the current relative to the voltage (assume the voltage is the reference phase)
  2. recca02

    Senior Member

    Apr 2, 2007
    Thats a very bold question...

    capacitive reactance = Xc= 0.5ųF x frequency
    Inductive reactance = XL= 130ųF x frequency

    add all resistance and reactances in series (and for parallel do the same you do for resistances in parallel)...remember we are dealing with AC here and hence it will be solved in either polar or rectangular form.
    rectangular form
    so total impedance Z = R + j(XL - Xc)

    I = V/Z

    you will need to learn a little about how mathematical operations are done on complex numbers or polar them...
    the angle you get in I in polar form(I<phi) will be the phase difference.
  3. silvrstring

    Active Member

    Mar 27, 2008
    Your capacitive reactance will be 1/(2pi*frequency*capacitance), and your inductive reactance will be XL=2pi*frequency*inductance. Everything else Recca said is right. They probably made a typo. Then find impedance Z as Recca said.

    Before you can find I=V/Z, it might be easier if you convert Z to polar form. If Zrect=R+jX, and you want to convert to Zpolar, Zpolar=sqrt(R^2+X^2) with angle theta = inverseTan(X/R).

    Divide E by Z as usual. Subtract denominator angle from numerator angle. You're done.

    I suggest you take Recca's advice. Understanding complex numbers, both rectangular and polar form, will make your life much easier.
  4. hgmjr

    Retired Moderator

    Jan 28, 2005
    Here is a link to the AAC ebook on complex numbers. Read up on this and then see if you can take a stab at your assignment.