$V =\frac{ Q }{2 C }$
Energy in each capacitor $=\frac{1}{2} CV ^{2}=\frac{1}{2} C \left(\frac{ Q }{2 C }\right)^{2}=\frac{1}{4}\cdot \frac{1}{2} \left(\frac{ Q ^{2}}{2 C }\right) =\frac{ U }{4}$


| Capacitor | Capacitance |
| $(A)$ Cylindrical capacitor | $(i)$ ${4\pi { \in _0}R}$ |
| $(B)$ Spherical capacitor | $(ii)$ $\frac{{KA{ \in _0}}}{d}$ |
| $(C)$ Parallel plate capacitor having dielectric between its plates | $(iii)$ $\frac{{2\pi{ \in _0}\ell }}{{ln\left( {{r_2}/{r_1}} \right)}}$ |
| $(D)$ Isolated spherical conductor | $(iv)$ $\frac{{4\pi { \in _0}{r_1}{r_2}}}{{{r_2} - {r_1}}}$ |



