In the given circuit, one of the $3\mu \mathrm{F}$ capacitors has $600\mu \mathrm{J}$ of energy. Then the potential difference across $2\mu \mathrm{F}$ capacitor is

Four metallic plates each of area $A$ and separated from one another by a distance $d$ are arranged as shown in the figure. What is the capacitance between $X$ and $Y ?$

In the circuit diagram shown in the adjoining figure, the resultant capacitance between $P$ and $Q$ is

In the given circuit, one of the $3\mu \mathrm{F}$ capacitors has $600\mu \mathrm{J}$ of energy. Then the potential difference across $2\mu \mathrm{F}$ capacitor is