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