The energy of a charged capacitor resides in

The energy stored in a condenser of capacity $C$ which has been raised to a potential $V$ is given by

If the potential of a capacitor having capacity of $6\,\mu F$ is increased from $10\, V$ to $20\, V$, then increase in its energy will be

$A$ $2$ $\mu F$ capacitor is charged to a potential $=$ $10\,V$. Another $4$ $\mu F$ capacitor is charged to a potential $=$ $20\,V$. The two capacitors are then connected in a single loop, with the positive plate of one connected with negative plate of the other. What heat is evolved in the circuit?......$\mu J$

A parallel plate capacitor of capacitance $C$ is connected to a battery and is charged to a potential difference $V$. Another capacitor of capacitance $2C$ is connected to another battery and is charged to potential difference $2V$. The charging batteries are now disconnected and the capacitors are connected in parallel to each other in such a way that the positive terminal of one is connected to the negative terminal of the other. The final energy of the configuration is

A $12 \;pF$ capacitor is connected to a $50 \;V$ battery. How much electrostatic energy is stored in the capacitor?