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Math in physics help

  1. Mar 28, 2005 #1
    In a certain RLC circuit, the rms current is 6.72A, the rms voltage is 230V, and the current leads the voltage by 55.9 Degrees.
    a)what is the resistance of the circuit?
    b)calculate the total XL-Xc
    c)Calc. the average power dissipated in the circuit.

    a) 1.92E1 Ohms
    c)8.665E2 J

    I can't figure out b! I tried using

    tan x = X/R
    tan 55.9 = (Xl-Xc)/(1.92E1 Ohm)
    But this did not give me the right answer...maybe i am just doing the math wrong here....would you do this to solve for (XL-Xc)?
    (1.92E1 Ohm)tan 55.9 = "x" ?
  2. jcsd
  3. Mar 28, 2005 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    Your approach is right.

    I get 28.36 ohms.

    Note: The power is in units of energy / time. [itex]VIcos\phi = P = I^2R[/itex], so it is 867 J/sec.

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