For the displacement current through the plates of a parallel plate capacitor of capacitance $30 \mu \mathrm{~F}$ to be $150 \mu \mathrm{~A}$, the potential difference across the plates of the capacitor has to vary at the rate of

A capacitor of capacitance $(4.0 \pm 0.2) \mu \mathrm{F}$ is charged to a potential of $(10.0 \pm 0 \mathrm{l}) \mathrm{V}$. The charge on the capacitor is

Two capacitors of capacitances $1 \mu \mathrm{~F}$ and $2 \mu \mathrm{~F}$ can separately withstand potentials of 6 kV and 4 kV respectively. The total potential, they together can withstand when they are connected in series is

A $10 \mu \mathrm{~F}$ capacitor is charged by a 100 V battery. It is disconnected from the battery and is connected to another uncharged capacitor of capacitance $30 \mu \mathrm{~F}$. During this process, the electrostatic energy lost by the first capacitor is