The magnitude of electric field E in the annular region of a charged cylindrical capacitor:

The magnitude of electric field in the annular region of a charged cylindrical capacitor is given by $\mathrm{E}=\frac{1}{2{\mathrm{\pi \epsilon }}_0}\frac{\mathrm{\lambda }}{\mathrm{r}}$ where $\mathrm{\lambda }$ is the charge per unit length and r is the distance from the axis of the cylinder. Thus $\mathrm{E}\propto \frac{1}{\mathrm{r}}.$