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Homework Help: What is the energy stored in the capacitor?

  1. Mar 6, 2006 #1
    20 J is placed across a 15uF capacitor. What is the energy stored in the capacitor?

    any ideas on how to do this?
  2. jcsd
  3. Mar 6, 2006 #2

    Andrew Mason

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    Check the question. I think it should be 20 volts not 20 J. (If 20 J is added to the capacitor, the energy stored in the capacitor is 20 J. because there is no energy is lost due to resistance).

    The energy is [itex]\int_0^q Vdq[/itex] where V = potential (energy/charge) between the plates of the capacitor. It is 0 Volts initially but increases to 20 V. when fully charged.

    Use the relationship between V and Q in a capacitor to express dq in terms of dV and then integrate with respect to V over the range 0 to 20 V.

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