Question

Two thin flat metal plates having large surface area are charged separately to acquire charge densities $+\sigma$ and $-\sigma$. The plates are then brought near to each other and held parallel to each other (Fig.) : If $E_A,E_B$ and $E_C$ denote the electric fields at the points $A,B$ and $C$ respectively, then which of the following will be true :

• A. $E_A=E_C=\frac{\sigma }{{\epsilon }_0}$
• B. $E_A=E_B=E_C=\frac{\sigma }{{\epsilon }_0}$
• C. $E_A=E_C=0,E_B=\frac{\sigma }{{\epsilon }_0}$
• D. $E_A=E_C=0,E_B=\frac{2\sigma }{{\epsilon }_0}$

Answer 1

Answer: (C)

$E_A=\frac{\sigma }{2{\epsilon }_0}-\frac{\sigma }{2{\epsilon }_0}=0$
$E_C=0,$
$E_B=\frac{\sigma }{2{\epsilon }_0}+\frac{\sigma }{2{\epsilon }_0}=\frac{\sigma }{{\epsilon }_0}$.