The figure shows three infinite non-conducting plates of charge perpendicular to the plane of the paper with charge per unit area `+sigma, +2sigma` and `-sigma`. Find the ratio of the net electric field at that point a to that at point B.

Answer

zero

Explanation

Charge on outer plates `=(sigmaA+2sigmaA-sigmaA)/2=sigmaA`
Charge distribution
Field at A: `E_(A)=0`
Field at B :
`E_(B)=(2sigma)/epsilon_(0) :. E_(A)/E_(B)=0`