\(I_d=\varepsilon_0 A \frac{d E}{d t}=\varepsilon_0\left(\pi R^2\right) \frac{d E}{d t}=i\)

\(I_d^{\prime}=\varepsilon_0\left(\pi R^2-\frac{\pi R^2}{4}\right) \frac{d E}{d t}\)

\(=\frac{3}{4} \varepsilon_0 \pi R^2 \frac{d E}{d t}\)

\(I_d=\frac{3}{4} i\)