11.0 Energy Density ($u$)

  Capacitors

    11.0 Energy Density ($u$)

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11.0 Energy Density ($u$)The potential energy per unit volume is called the energy density ($u$). The energy density in dielectric medium is given by,$$u = \frac{1}{2}{\varepsilon _ \circ }K{E^2}$$ This relation shows that the energy stored per unit volume depends on ${E^2}$. If $E$ is the electric field in a space of volume $dV$, then the total stored energy in electrostatic field is given by,$$u = \frac{1}{2}{\varepsilon _ \circ }K\int {{E^2}dV} $$ and $E$ is uniform thoughout the volume (electric field between the plates of a capacitor is uniform), then the total stored energy can be given by,$$U = \frac{1}{2}{\varepsilon _ \circ }K{E^2}V$$