# Skin Depth Calculator

Skin depth calculator is a tool used to find out the skin depth in the conductor. The depth of the conductor up to which current flows is known as the Skin Depth. The symbol of skin depth is δ.

## What is the Skin Effect?

An alternating electric current does not flow in the entire cross-section of a conductor. This happens because of Skin Effect. In the case of AC, the current density is highest near the surface of the conductor and decreases exponentially as distance from the surface increases. The skin effect phenomenon is absent in the case of DC because frequency of DC voltage or current is zero.

The AC resistance of the conductor depends on the supply frequency of voltage or current. The higher frequency current tends to flow on the surface of the conductor. The reason is that there is more charge concentration near the surface of the conductor. The charge concentration reduces from surface to the inner side of the conductor. The charge concentration is maximum at the surface and zero at the center of conductor. The skin depth (δ) is a point at which the current density reaches approximately 37% of the charge concentration at the surface of the conductor.

The skin depth changes with a change in frequency , relative permeability, and resistivity of conductor.

## Solved problem on Skin Depth

Calculate the skin depth for the copper conductor that carries 50 kHz.
Conductivity of copper conductor ρ = 1.78 X 10-6 Ω-m
Relative Permeability of copper μr = 0.999991

## Applications of Skin Depth

Skin depth shows the region of the conductor that carries majority of current. The current flows up to the skin depth of the conductor. If we use large diameter conductor and current flows up to 30 % of its depth, than the 70 % of depth does not carry current. Therefore, in this case it is not economic to use a large diameter conductor.

Thus, it is possible to economically design a conductor for a particular application by calculating the skin depth of the conductor. For example, skin depth of the copper conductor for RF signal operating at 2.5 GHz is about 1.32 μm. Even, a large portion of a small wire size of about 30 AWG( 7.62 μm) remains unutilized , and the current flows up to the depth of 1.32 μm.