Electric Flux

Flux refers to the flow or stream of anything from one point to another point. 

Electric flux is the total number of lines of force passing through the unit area of a surface held perpendicularly.

Mathematically the electric flux is defined as: The dot product of electric field intensity  $\left (\vec{E} \right )$  and the vector area  $\left (\vec{\Delta S} \right )$  is called electric flux.

\[\therefore \Delta \phi =\vec{E}.\vec{\Delta S} =E\Delta S Cos\Theta\] 

Electric Flux

1. The flux will be maximum when the vector area is parallel to the electric field. 
\[\because \Theta =0, \Rightarrow Cos\Theta =1 \\ \therefore \Delta \phi =E\Delta S Cos\Theta=1\]
2. The flux will be Minimum (zero) when the vector area is perpendicular to the electric field
\[\because \Theta =90^{0}, \Rightarrow Cos\Theta =0 \\ \therefore \Delta \phi =E\Delta S Cos\Theta=0\]

The unit of electric flux is N C^–1 m².