capacitance problem

Discussion in 'Physics' started by logearav, Oct 8, 2011.

  1. logearav

    Thread Starter Member

    Aug 19, 2011
    A dielectric of dielectric constant 3 fills three fourth of the space between plates of a parallel plate capacitor. What percentage of the energy is stored n the dielectric?
    My attempt to solve this is given in attachment.
    The answer is given as 50%. I don't know how to arrive that. Please help revered members
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    C1 is the free space capacitance
    C2 is the filled space capacitance

    C1 & C2 are effectively in series

    C_1=\frac{\epsilon_0 A}{d/4}=\frac{4\epsilon_0 A}{d}

    C_2=\frac{3\epsilon_0 A}{3d/4}=\frac{4\epsilon_0 A}{d}

    Where A is the plate area and d is the total plate separation distance.

    So C1=C2

    Being equal and in series they will each have half of the total voltage applied to the capacitance.

    Having equal voltage & equal capacitance means they have equal energy - so they share half the total energy stored on their combined equivalent series capacitance.
    Last edited: Oct 8, 2011
  3. logearav

    Thread Starter Member

    Aug 19, 2011
    Thanks for the reply t_n_k. C1 and C2 are connected in series--is it implied?