Assume that A (SI unit: m ) is a small surface centered at a given point M and orthogonal to the motion of the charges at M. If IA (SI unit: A) is the electric current flowing through A, … See more

Free currents
Charge carriers which are free to move constitute a free current density, which are given by expressions … See more

In electrical wiring, the maximum current density (for a given temperature rating) can vary from 4 A⋅mm for a wire with no air circulation around it, to over 6 A⋅mm for a wire in free air. Regulations for building wiring list the maximum allowed current of each size of cable … See more

Current density is important to the design of electrical and electronic systems.
Circuit performance depends strongly upon the designed current level, and the current density then … See more

Since charge is conserved, current density must satisfy a continuity equation. Here is a derivation from first principles.
The net flow out of some volume V (which can have an arbitrary … See more

• Hall effect
• Quantum Hall effect
• Superconductivity
• Electron mobility
• Drift velocity See more