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Capacitance Current and Power

  1. Sep 30, 2013 #1
    1. The problem statement, all variables and given/known data

    The voltage across a capacitor with a value of 0.01 Farads is v(t) 100*cos(2pi60t). Find i(t),p(t),and w(t).

    2. Relevant equations

    i(t)=Cv'(t) [current]
    p(t)=i(t)v(t) [power]
    w= integral of p(t) [Energy stored over time]

    3. The attempt at a solution

    I was able to correctly determine the current of capacitance, -120*pi*sin(2pi60t) Amperes. However, this multiplied by the voltage, does NOT equal the given answer of -18,850sin(2pi120t) Watts.

    Could someone please clear this up for me? I would've used proper symbols, but the test is quite shortly, no time to mess with that ... :/

  2. jcsd
  3. Sep 30, 2013 #2


    User Avatar
    Science Advisor

    Try using a trig identity for Sin(2X).
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