Question 1

What units does this converter support?

Accepted Answer

The converter covers 24 units across three systems. SI / Metric (14 units): A/m (SI base), kA/m, mA/m, μA/m, nA/m, A/cm, A/mm, A/km, kA/cm, mA/cm, mA/mm, μA/cm, μA/mm, nA/cm. Imperial / US (6 units): A/in, A/ft, A/yd, mA/ft, mA/in, kA/in. CGS (4 units): abA/m, abA/cm, abA/in (EMU system), and statA/cm (ESU/Gaussian system).

Question 2

What is linear current density and where is it used?

Accepted Answer

Linear current density (symbol K or J_s) is the electric current per unit width flowing in a thin sheet or along a surface, expressed in amperes per meter (A/m). It is fundamental in electromagnetics and electrical engineering. Key applications include: surface current analysis on perfect conductors and antenna elements using boundary conditions (K = n̂ × H, where H is the magnetic field at the surface); modelling current distribution in transmission line shields and PCB ground planes; magnetostatics and the equivalent surface current model for permanent magnets; microwave and RF waveguide design; superconductor critical current calculations; and transformer winding analysis.

Question 3

Why is A/m the standard unit in electromagnetics?

Accepted Answer

A/m (amperes per meter) is the SI unit for both linear current density (K, current per width) and magnetic field intensity (H), which are intimately related via Ampere's boundary condition: the discontinuity in H at a surface equals the surface current density K. Most textbooks (Hayt, Griffiths, Pozar) use A/m as the natural unit. mA/m is common for antenna radiation analysis and small signal electromagnetics. kA/m is used for permanent magnets, inductors, and high-field applications. PCB and IC design often uses A/mm or mA/mm for trace-level current density.

Question 4

What are the CGS units (abA and statA) and when are they used?

Accepted Answer

The CGS system has two subsystems for electromagnetism. The EMU (electromagnetic) subsystem uses the abampere: 1 abampere = 10 amperes (exact). abA/m and abA/cm appear in older physics literature and some specialized EM texts. The ESU (electrostatic) or Gaussian subsystem uses the statampere: 1 statampere ≈ 3.3356 × 10⁻¹⁰ amperes. statA/cm is the natural unit for current density in the Gaussian system. These units appear in classical electrodynamics textbooks (Jackson, Griffiths), plasma physics literature, and astrophysics.

Question 5

How does linear current density relate to magnetic field intensity?

Accepted Answer

For a flat current sheet with linear current density K (A/m), the boundary condition at the sheet surface is K = n̂ × (H₁ − H₂), where H₁ and H₂ are the magnetic field intensities on each side and n̂ is the surface normal. For an infinite sheet carrying K, the H field above and below is H = K/2 (directed parallel to the sheet, perpendicular to current). This models PCB ground planes, coaxial cable shields, and the equivalent surface current of a uniformly magnetized permanent magnet (K_eq = M × n̂, where M is the magnetisation in A/m).

Question 6

What are typical linear current density values in real systems?

Accepted Answer

Representative values: PCB trace (100 mA in 1 mm trace width) - 100 mA/mm = 100 A/m. Permanent magnet equivalent surface current - 100–2000 kA/m. Antenna radiating element surface current - 1–100 mA/m. Superconductor critical current density - 1–100 kA/mm. HF induction coil surface current - 10–500 A/m. RF microstrip ground plane - 1–50 A/m. These values help verify that a computed result is physically reasonable.

Question 7

How do I convert in the other direction?

Accepted Answer

Hover any result row and click the swap icon (⇅) to use that unit and value as the new input, reversing the conversion instantly. You can also click the ⇄ button between the From and To fields to swap both units while updating the value.

Question 8

Is my data private?

Accepted Answer

Yes - all conversions run entirely in your browser using JavaScript and exact NIST-traceable conversion factors. No data is ever sent to any server.

Linear Current Density Converter

How to Use

Features

Frequently Asked Questions

/ related tools

Community Feedback

Reviews

Rate & Review

/ share this tool