- (d) Zero.
Explanation:
There are two plates A and B having surface charge densities,

$\sigma_\text{A}=17.0\times10^{-22}\text{C/m}^2$
on A and $\sigma_\text{B}=-17.0\times10^{-22}\text{C/m}^2$on B, respectively. According to Gauss' theorem, if the plates have same surface charge density but having opposite signs, then the electric field in region I is zero.
$\text{E}_\text{I}=\text{E}_\text{A}+\text{E}_\text{B}$
$=\frac{\sigma}{2\in_0}+\Big(-\frac{\sigma}{2\in_0}\Big)=0$
- (d) Zero.
Explanation:
The electric field in region III is also zero.
$\text{E}_\text{III}=\text{E}_\text{A}+\text{E}_\text{B}$
$=\frac{\sigma}{2\in_0}+\Big(-\frac{\sigma}{2\in_0}\Big)=0$
- (c) 1.9 × 10-10 N/C
Explanation:
In region II or between the plates, the electric field.
$\text{E}_\text{II}=\text{E}_\text{A}-\text{E}_\text{B}$
$=\frac{\sigma}{2\in_0}+=\frac{\sigma}{2\in_0}$
$=\frac{\sigma(\sigma_\text{A}\text{ or }\sigma_\text{B})}{\in_0}=\frac{17.0\times10^{-22}}{8.85\times10^{-12}}$
E = 1.9 × 10-10 N/C
- (c) 1 : 1
Explanation:
Since electric field due to an infinite-plane sheet of charge does not depend on the distance of observation point from the plane sheet of charge. So, for the given distances, the ratio of E will be 1 : 1.
- (b) Spherical.
Explanation:
ln order to estimate the electric field due to a thin finite plane metal plate, we take a cylindrical cross-sectional area A and length 2r as the gaussian surface.