Electric flux and area vector

Electric flux and area vector

In this topic we will discuss about Electric flux and area vector .

question may be asked as what is electric flux ? write its unit and dimension.

Area vector and electric flux –

As we know area is a scaler quantity , but in some cases or in case of some problems area is taken as vector quantity . the direction of area is taken as the normal of the surface at a given point . The vector associated with every area element of a closed surface is taken to be in the direction of the outward drawn normal .


Electric flux – Electric flux over an area in an electric field is the total number of field line passes through that area normally .  It is denoted by ɸ its unit is Nm2C-1 . And its dimension is  [M1L3T-3A-1]. Electric flux is a scaler quantity.

The  number of electric field lines crossing this area is  proportional to field intensity E . Let electric field lines makes an angle ϴ with the area vector dS , and E is the electric field intensity , then we can write  dɸ =  E. (dS cosϴ ) [ since dScosϴ is the component of area vector normal to the surface ].

So ,  dɸ = E dS (With vector sign).

Or,  ɸE = ∫E dS cosϴ

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