A model for current distribution in a conductor is that for a homogenous conducting half space with surface current parallel to the interface. Current density at depth d is given by the expression \(J=J_0 \cdot e^{(-(1+\jmath ) \cdot \frac dδ)}\) where δ is the skin depth \(δ=(ω \cdot µ \cdot σ)^{0.5}\), σ is the conductivity). This is a model for a plane wave in an infinite block of conductor, so there are some issues caused by curvature of the wire surface, more so towards the centre.

## Copper round conductor – 1.024mm (#18) single core

Fig 1 is a plot of the current distribution in a 1mm dia (#18) round copper conductor at 1.8MHz as implied by the model. Note that while the magnitude of current decays exponentially with depth, there is an imaginary component that hints a curl of the E and H fields within the conductor. Continue reading A model of current distribution in copper clad steel conductors at RF