- #1

beowulf.geata

- 12

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## Homework Statement

A thin metallic strip on a circuit board has length L, width a and thickness t, with L>>a>> t. Derive an expression for the resistance between the ends of the strip at frequency f, assuming that the skin depth is small compared with the thickness t.

## Homework Equations

The book where I took this problem from explains that for an electromagnetic wave polarized in the x-direction and traveling in the z-direction through a conducting medium where ω << 1/τ

_{c}(1/τ

_{c}being the frequency of collisions between an electron and the lattice) the electric field is the real part of

**E**= E

_{0}e

^{-z/δ}e

^{i(z/δ-ωt)}

**e**

_{x}(where δ is the skin depth).

## The Attempt at a Solution

What I am puzzled by is that the solution says that the current density is

J(z)= σE(z) = σE

_{0}e

^{-z/δ},

so my question is: where has the real part of e

^{i(z/δ-ωt)}gone?

I'd be very grateful for any pointers on this.