An electric field of two positively charged parallel plates:
Two thin plane-parallel sheets of charge having uniform charge densities σ1 and σ1 with σ1>σ2>0Suppose r^ is a unit vector pointing from left to right.
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In region (I): Field due to the two sheets are
E1−→=−σ12ϵ0r^...and..E2−→=−σ22ϵ0r^
from the principle of superposition the total electric field at any point of the region, I is
EI−→=E1−→+E2−→=−r^σ1+σ22ϵ0
In Region (II): Field due to the two sheets are
E1−→=σ12ϵ0r^...and...E2−→=−σ22ϵ0r^
EII−→−=E1−→+E2−→=r^σ1−σ22ϵ0
In Region (III): Field due to the two sheets are
E1−→=σ12ϵ0r^...and...E2−→=σ22ϵ0r^
EIII−→−=E1−→+E2−→=r^σ1+σ22ϵ0
σ