12CV2\frac{1}{2} C V^{2}21CV2
Q22C\frac{Q^{2}}{2 C}2CQ2
ϵ022E0\frac{\epsilon 0^{2}}{2 E_{0}}2E0ϵ02
12ϵ0E2\frac{1}{2} \epsilon_{0} E^{2}21ϵ0E2