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Capacitor, Charge, and Sinewave, need help please

  1. Mar 30, 2015 #1
    1. The problem statement, all variables and given/known data

    A capacitor C is charged to an initial potential of 70.0 V, with an initial charge of Q0. It is in a circuit with a switch and an inductor with inductance L = 4.03×10-2 H and resistance RL.

    At t=0, the switch is closed, and the curve below shows the potential V across the capacitor as a function of time t.

    https://s4.lite.msu.edu/cgi-bin/plot.png?file=jonesb63_msu_1427749730_13825679_plot.data [Broken]

    Calculate the energy in the circuit after a time of 16 periods. Note that the curve passes through a grid intersection point.

    Calculate the time required for 86% of the initial energy to be dissipated.


    3. The attempt at a solution

    media%2F8f4%2F8f40d080-e8e7-46ef-8ed5-b79a27de2fea%2FphpPOHOPO.png

    media%2F3cf%2F3cfa6b6a-758d-4580-a16b-852e1d994a33%2FphpsCHPxR.png

    media%2F9de%2F9dea4368-d50e-47bb-9e2d-dc043892efa2%2FphpUpSWtr.png
    Not sure what is wrong with this.
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Mar 30, 2015 #2

    phyzguy

    User Avatar
    Science Advisor

    I haven't looked through everything, but your calculation of the period is clearly incorrect. The sine wave passes through zero at t=0.7ms, but it is not zero at t=0. So the time between t=0 and t=0.7 is not a whole number of periods.
     
  4. Mar 30, 2015 #3
    oh 12.5 per second yeah my bad, thanks
     
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