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Homework Help: Instantaneous current in a reisistor, capacitor and inductor

  1. Nov 27, 2012 #1
    1. The problem statement, all variables and given/known data
    a resistor, a capacitor and an inductor are connected in parallel to a source of oscillating EMF of frequency 955hz and amplitude of 1.0x10^3 V. the resistance of the resistor is 200Ω. what is the maximal instantaneous current in the resistor? if we want to make a maximum instantaneous currents in the capacitor and in the inductor equal to that in the resistor, what values of the capacitance and the inductance must we select?

    2. Relevant equations
    Irms= ΔVrms/(R^2+(xl-xc)^2)^(1/2)
    Irms= Imax/(2)^(1/2)= 0.707Imax
    frequency= 955hz (2∏f)

    3. The attempt at a solution
    amplitude is given, therefore, we can consider this Vmax

    Irms= 1.0x10^3V/ (200^2+(xl-xc)^2)^(1/2)
  2. jcsd
  3. Nov 27, 2012 #2


    User Avatar

    Staff: Mentor

    For instantaneous values you won't need to deal with rms values. You'll want the instantaneous peaks of the voltages and/or currents.

    If the input voltage is 1000V*cos(ωt), what's the maximum voltage that can appear across the resistor?
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