Question

1) Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude $17.0\times {10}^{-22}c/m^2$ What is $E$:
A) in the outer region of the first plate

2) Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude $17.0\times {10}^{-22}c/m^2$ What is $E$:
B) in the outer region of the second plate

3) Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude $17.0\times {10}^{-22}c/m^2$ What is $E$:
C) between the plates

Answer 1

1) In the outer region of plate 𝐴 i.e., region $I$, electric field is zero since the charge enclosed is zero. Also electric field due to two plates will be equal (since plates are close to each other) and opposite in that region.


2) In the outer region of plate $B$ i.e., region $III$, electric field is zero since the charge enclosed is zero. Also electric field due to two plates will be equal (since plates are close to each other) and opposite in that region.


3) Let surface charge density on plate A, ${\sigma }_A=+17.0\times {10}^{-22}C/m^2$

Surface charge density on plate B, ${\sigma }_B=-17.0\times {10}^{-22}C/m^2$

Net electric field in between the plates i.e region $II$,

$E=\frac{\sigma }{2{ϵ}_o}+\frac{\sigma }{2{ϵ}_o}=\frac{\sigma }{{ϵ}_o}$

$E=17.0\times {10}^{-22}\times 4\pi \times 9\times {10}^9$

$E=1.92\times {10}^{-10}N/C$