Electric Flux

Electric flux over an area can be defined as the total number of electric field lines crossing through that area.

• Its SI unit is NC^-1m².

• The number of electric field lines crossing perpendicular to the area element is proportional to EΔS.

• The projection of the area element normal to E is ΔScosθ.

• The number of field lines crossing ΔS is proportional to EΔScosθ.

• When θ = 90⁰, field lines will be parallel to ΔS and will not cross it at all.

• The direction of a planar area vector is along its normal.

• Conventionally, for a closed surface, the direction of an area vector is outward normal.

Electric flux crossing through a small area element is given by

Total flux through a surface is