# A $30\: pF$ capacitor has circular plates of area $100\: cm^2$. It is charged by a $70\: V$ battery through a $2\Omega$ resistor. At the instant, the battery is disconnected; the electric field between the plates is changing most rapidly. At this instant, find the rate of change of electric field between the plates.
$\begin {array} {1 1} (a)\;39.5 \times 10^{12} \: V/ms & \quad (b)\;3.95 \times 10^{12} \: V/ms \\ (c)\;39.5 \times 10^{14} \: V/ms & \quad (d)\;3.95 \times 10^{14} \: V/ms \end {array}$