lederstrøm

Lederstrøm is a term used in physics and electrical engineering to describe the flow of electric charges through a conductive material due to an electric field. In common usage it corresponds to conduction current, or drift current, the component of electric current carried by mobile charge carriers such as electrons (and holes in semiconductors) under the influence of an electric field. The conventional direction of lederstrøm is the direction in which positive charges would move; in metals electrons actually drift in the opposite direction.

At the macroscopic level, the current density J is related to the electric field E by Ohm’s law, J = σE, where σ is the electrical conductivity of the material. The total current i in a conductor with cross-sectional area A is i = J·A, and for a simple resistor this yields Ohm’s law i = V/R. Microscopically, current density can be expressed as J = nqvd, where n is the carrier density, q is the elementary charge, and vd is the drift velocity of the carriers.

In different materials, lederstrøm can comprise more than a single mechanism. In dielectrics and time-varying fields, displacement current accounts for changing electric fields as described by Maxwell’s equations. In semiconductors, drift current and diffusion current (due to concentration gradients) both contribute to the total current, i.e., J = J_drift + J_diffusion.

Lederstrøm is a foundational concept in circuit analysis, conductor theory, and solid-state physics, underpinning the operation of resistors, wires, transistors, and many other electronic devices. See also Ohm’s law, conduction current, diffusion current, and displacement current.