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Series Resonance

Discussion in 'Homework Help' started by hazbestoz, Apr 13, 2004.

  1. hazbestoz

    Thread Starter New Member

    Apr 13, 2004
    Help! I've done a lab project on something I don't have a clue about! I now have to write up the report and this is where I am stuck!

    I was asked to alter the frequency and measure the voltage across a signal generator, capacitor (0.1μF), the load (0.1H) and across a 100Ω resistor (all on the same circuit in series) and at each frequency, the current. (The frequencies that I used varied from 1200Hz to 2200Hz, six readings in total.)
    I've then been asked to plot the impendance-ratio, power factor and phase angle against frequency.
    I was wondering if someone could talk me through how I am supposed to find these results?!
    Thanks very much, a very confused (and getting frustrated) student! :wacko:
  2. Battousai

    Senior Member

    Nov 14, 2003
    Begin by finding the impedance of the tank.

    You're going to get a complex number that depends on frequency.

    The magnitude of that number is your impedance at a given frequency (mag^2 = real^2 + imag^2).

    The phase of that number is your phase angle at a given frequency (tan (phase) = imag/real).

    I'm not sure what the power factor is.
  3. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    niceexplanation battousai. let me add a little; impedance is the combination or resistance and reactance and the phase angle (ø) between the voltage and current is between 0 and ±90*. the power factor is the ration of the true power given by ( IsqrdR) dissipated in the resistance to the apparent power (S) which is the current/voltage product of the circuit, neglecting the phase difference current and voltage.

    Fp = cos ø = P / S ø is the phase angle between the circuit voltage and current

    your power factor will depend on the state of your circuit, whether the current lags or leads the voltage.
  4. Dave

    Retired Moderator

    Nov 17, 2003
    Correct, the Power Factor means nothing unless you state whether it is "leading" or "lagging". Try leaving it out an see how they wrap your knuckles! ;)