Q=CV\] when it is connected with ANOTHER uncharged capacitor. \[{{V}_{c}}=\frac{{{q}_{1}}+{{q}_{2}}}{{{C}_{1}}+{{C}_{2}}}=\frac{q+0}{C+C}\] \[{{V}_{c}}=\frac{V}{2}\] Initial ENERGY \[{{U}_{i}}=\frac{1}{2}C{{V}^{2}}\] Final energy \[{{U}_{f}}=\frac{1}{2}C{{\left( \frac{V}{2} \right)}^{2}}+\frac{1}{2}C{{\left( \frac{V}{2} \right)}^{2}}\] \[=\frac{C{{V}^{2}}}{4}\] Loss of energy \[={{U}_{i}}-{{U}_{f}}\] \[=\frac{C{{V}^{2}}}{4}\] i.e. decreases by a FACTOR