Figure 2: Graph of charge against
potential difference.
The capacitor is charged with
charge Q to a voltage V. If the capacitor is discharged by a little amount so
that the potential difference drops, δV, there is a resulting little energy
loss (δW). This can be worked out by moderating the equation above as
charge Q to a voltage V. If the capacitor is discharged by a little amount so
that the potential difference drops, δV, there is a resulting little energy
loss (δW). This can be worked out by moderating the equation above as
δW = δV X Q
If the capacitor is discharged
completely,
completely,
Energy Loss = Area of shaded
triangle
triangle
ΔW(for a capacitor charge or
discharge) = ½QV
discharge) = ½QV
But Q = CV
Therefore ΔW = ½CV
Or ΔW = ½Q/C
The maximum energy that can be
safely stored in a capacitor is limited by the maximun electric fiel that the
dielectric between the parallel plates can withstand before it breaks down.
Therefore, capacitors of the same type have the same maximum energy density
(joules of energy per cubic metre).
safely stored in a capacitor is limited by the maximun electric fiel that the
dielectric between the parallel plates can withstand before it breaks down.
Therefore, capacitors of the same type have the same maximum energy density
(joules of energy per cubic metre).
