Please note that this course has 56 minutes of video in it.

In this course, we will be discussing electric flux, how to calculate flux, as well as the analogy with the movement of water. Suppose there is flowing water through a pipe at a certain velocity in a certain direction, say, to the right. Suppose there is a small cross-sectional area of the pipe. Then the amount of liquid flowing through the area in the unit interval of time can be written as vds. Suppose the area is inclined at an angle with the direction of the movement, then the effective area for the computation of the movement is given as ds cosθ.

Similarly, an electric field is analogous to the movement of liquid in the analogy. But whereas liquid can be seen, the electric field cannot.

Electric flux is the number of electric field lines per second through a given area. Although the electric flux is only influenced by the charge inside a close surface, the net electric field (E) can be influenced even by the charge outside the surface. In all situations, the application of Gauss's law is possible but is more easily applied when the electric field is highly symmetrical, as in the case of a sphere or a cylinder.

The SI unit of electric flux is the volt-meter (V·m) or the newton-meter squared per coulomb (N·m²·C⁻¹). It can be written as kg·m³·s³·A⁻¹ in terms of SI base units.