Question

Two large, parallel conducting plates are placed close to each other. The inner surfaces of the two plates have surface charge densities $+\sigma$ and $-\sigma$. The other surfaces are without charge. The electric field has a magnitude of :

• A. $\frac{2\sigma }{{\epsilon }_0}$ in the region between the plates
• B. $\frac{\sigma }{{\epsilon }_0}$ in the region between the plates
• C. $\frac{\sigma }{{\epsilon }_0}$ in the region outside the plates
• D. zero in the region outside the plates

Answer 1

Answer: (B), (D)

The correct options are
B $\frac{\sigma }{{\epsilon }_0}$ in the region between the plates
D zero in the region outside the plates

The electric field in between the plate is $E_{center}=\frac{\sigma }{2{ϵ}_0}+\frac{\sigma }{2{ϵ}_0}=\frac{\sigma }{{ϵ}_0}$
Outside of the plates the electric field is $E=\frac{\sigma }{2{ϵ}_0}-\frac{\sigma }{2{ϵ}_0}=0$