Q = C V {\displaystyle Q=CV} defines capacitance.
C = ε 0 A d {\displaystyle C=\varepsilon _{0}{\tfrac {A}{d}}} where A is area and d<<A1/2 is gap length of parallel plate capacitor
Series : 1 C S = ∑ 1 C i . {\displaystyle {\text{Series}}:\;{\tfrac {1}{C_{S}}}=\sum {\tfrac {1}{C_{i}}}.} Parallel: C P = ∑ C i . {\displaystyle {\text{ Parallel:}}\;C_{P}=\sum C_{i}.}
u = 1 2 Q V = 1 2 C V 2 = 1 2 C Q 2 {\displaystyle u={\tfrac {1}{2}}QV={\tfrac {1}{2}}CV^{2}={\tfrac {1}{2C}}Q^{2}} = stored energy
u E = 1 2 ε 0 E 2 {\displaystyle u_{E}={\tfrac {1}{2}}\varepsilon _{0}E^{2}} = energy density
defines capacitance.
where A is area and d<<A1/2 is gap length of parallel plate capacitor
= stored energy
= energy density