Two capacitors of $3 \mu \mathrm{~F}$ and $6 \mu \mathrm{~F}$ are connected in series and a potential difference of 900 V is applied across the combination. They are then disconnected and reconnected in parallel. The potential difference across the combination is

The minimum value of effective capacitance that can be obtained by combining 3 capacitors of capacitances $1 \mathrm{pF}, 2 \mathrm{pF}$ and 4 pF

A system of two capacitors of capacitance $2 \mu \mathrm{~F}$ and $4 \mu \mathrm{~F}$ is connected in series across a potential difference of 6 V . The electric charge and energy stored in a system are