Three large conducting sheets placed parallel to each other at a finite distance contain charges `Q,-2Q, and 3Q`, respectively. Find the electric fields at points A, B, C, and D.

Explanation

`E_(A)=E_(Q)+E_(-2Q)+E_(3Q)`. (i) Here `E_(Q)` means electric field due to 'Q'.
`E_(A)=((Q-2Q+3Q))/(2A epsilon_(0))=(2Q)/(2Aepsilon_(0))=(Q)/(A epsilon_(0))` towards left
(ii) `E_(B)=(Q-(-2Q+3Q))/(2Aepsilon_(0))` towards right `=0`
(iii) `E_(C)=((Q-2Q)-(3Q))/(2Aepsilon_(0))=(-4Q)/(2Aepsilon_(0))=(-2Q)/(Aepsilon_(0))` towards right `rArr (2Q)/(Aepsilon_(0))` towards left
(iv) `E_(D)=((Q-2Q+3Q))/(2Aepsilon_(0))=(2Q)/(2Aepsilon_(0))=(Q)/(Aepsilon_(0))` towards right