Answer
$ 144\ pF$
Work Step by Step
It is given that:
Radius of each plate$ =8.20\ cm = 8.20 \times 10^{-2} m$
Separation between the plates $ d = 1.30 mm = 1.30\times 10^{-3}\ mm $
Area of the circle $A = \pi r^2 = \pi (8.20 \times 10^{-2}\ m )^2 = 2.11\times 10^{-2}\ m^2$
The formula for the capacitance having area $A$ and distance separation $d$ is;
$C =\frac {\epsilon_o A}{d}$
$C =\frac {(8.85\times 10^{-12}\ c^2/N.m^2)(2.11\times 10^{-2}\ m^2)}{1.30\times 10^{-3}\ m}$
$C = 144\times 10^{-12} F$
$C = 144\ pF$
