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Pros help me with physics hw

  1. Nov 18, 2008 #1
    1. The problem statement, all variables and given/known data

    hello everybody, i had hw prob due tommorrow, but i couldn't solve, the attached file is the image of the problem (it absolutely has no virus). all known values are labeled in the picture (V, R (same for all), C1 and C2). The questions are: find curren I, and time constant (which is equal to RC)

    2. Relevant equations
    I let my friend borrow my textbook, and i forgot to get his cell phone, so i can't find many formulas for the prob. But i do remember some and enough for the prob
    V1 =V2 for parallel, I = I1 + I2 for parallel, V = V1 + V2, I1 = I2....

    3. The attempt at a solution

    The prob involves RC circuit, if it's series RC circuit, i may (or may not) find the solutions, but here the parallel RC circuit, and i don't have textbook with me, so i couldn't find the connection between R and C in parallel circuit. I did surfing the web to find the formula, and i found the formula: Rc = j omega C (or Ic = j omega CV). I have no idea what j and omega are, beside, they are not given values, so i stuck.

    I believe the above formula only apply for AC circuit, while this problem is DC circuit. I was thinking that the current doesn't go through the capacitors, so we can calculate the total resistance R of the circuit while ignoring the capacitor, then we use the formula i(t) = U/R * [1-e^(-t / RC)] to find current I (i didn't find any source that say this formula could apply to parallel RC). That was my plan, if someone could point out the solution, million times thanx

    Attached Files:

    Last edited: Nov 19, 2008
  2. jcsd
  3. Nov 18, 2008 #2
    Last edited: Nov 18, 2008
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