Source

A point or region from which a field’s flux emerges. In vector calculus, a source is characterized by positive divergence, indicating net outward flow.

Divergence: A scalar measure of the net outward flow of a vector field per unit volume. Positive divergence is the local mathematical signature of a source.
Vector field: A function assigning a vector to each point in a space. Sources describe outward emergence within vector fields.
Point charge: An idealized electric charge concentrated at a single point. Positive point charges act as sources of the electric field.
Sink: A point or region into which a field’s flux converges. A sink has net inward flux, opposite to a source's outward flux.
Flux: The amount of a vector field passing through a surface per unit time or area, depending on convention. A source is identified by net flux emerging through a closed surface around it.
Scalar field: A function assigning a scalar value to each point in a space. Scalar potentials can generate fields whose divergence identifies sources.
Electric field: A vector field describing the electric force per unit positive charge. Electric-field lines emerge from positive charges, which are field sources.
Solenoidal vector field: A vector field whose divergence is zero everywhere. Such a field has no local sources or sinks.
Gauss's theorem: A theorem equating a vector field's flux through a closed surface to the integral of its divergence over the enclosed volume. It connects a source's local divergence to measurable outward flux.
Line integral: An integral that accumulates a function or vector field along a curve. Circulation and potential differences provide complementary ways to characterize fields.

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