Question

Electric field between two equally and similarly charged (+σ, surface charged density)

parallel plates is. (a) σ / є0

(b) σ /(2 є0)

(c) Zero

(d) Varying electric field​

Answer 1

Explanation:

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When discussing an ideal parallel-plate capacitor, σ usually denotes the area charge density of the plate as a whole - that is, the total charge on the plate divided by the area of the plate. There is not one σ for the inside surface and a separate σ for the outside surface. Or rather, there is, but the σ used in textbooks takes into account all the charge on both these surfaces, so it is the sum of the two charge densities.

σ=QA=σinside+σoutside

With this definition, the equation we get from Gauss's law is

Einside+Eoutside=σϵ0

where "inside" and "outside" designate the regions on opposite sides of the plate. For an isolated plate, Einside=Eoutside and thus the electric field is everywhere σ2ϵ0.

Answer 2

Answer:

At the midpoint of the line joining two equal point charges, the field is zero, and the electric field lines on this line joining the charges each begin at a charge and kind of end at the midpoint.