A parallel plate capacitor has surface density of r_s C/m². The dielectric inside capacitor is air. The electric field intensities outside and inside the capacitor are

In case of capacitor, the charges on two plates of capacitor are of opposite sign. We know that electric field due to infinite sheet charge with density r_s is Outside the capacitor, electric field intensities due to upper plate and lower plate cancel each other. ∴ E_outside = 0 Inside the capacitor, the electric field intensities due to upper and lower plate add together ∴