Definition:Flux/Direction

Definition

While flux is a scalar quantity, it does have a direction.

The sign of vector area $\delta S$ through which the flux operates depends upon the right-hand rule according to the direction of rotation around $S$ when describing it.

Hence, having decided on the sign of $\delta S$, the flux through $\delta S$ is either:

positive, where the angle $\psi$ between the normal to $\delta S$ is acute

negative, where the angle $\psi$ between the normal to $\delta S$ is obtuse.

That is:

a positive flux when $\delta S$ is oriented from left to right

is:

a negative flux when $\delta S$ is oriented from right to left.

Sources

• 1990: I.S. Grant and W.R. Phillips: Electromagnetism (2nd ed.) ... (previous) ... (next): Chapter $1$: Force and energy in electrostatics: $1.4$ Gauss's Law: $1.4.1$ The flux of a vector field