# Transmission Lines

Transmission lines are very important **historically** since they enabled the **communication** over long distances. Other than that, they are very interesting from a didactical perspective:

- one-dimensional systems that can be characterized by very
**few parameters** (in the end, it's only the impedance \(Z\))
- very good example for
**slowly varying fields** approximation, where \(\nabla\times\mathbf{B}\left(\mathbf{r},t\right)\approx\mu_{0}\mathbf{j}\left(\mathbf{r},t\right)\) and thus the coupling of electric and magnetic field is solely given by Faraday's law \(\nabla\times\mathbf{E}\left(\mathbf{r},t\right)=-\dot{\mathbf{B}}\left(\mathbf{r},t\right)\)
- fundamental physical effects like
**wave propagation** and **reflection** can be explained which will be a good bridge to complicated relativistic phenomena

With these facts in mind, we hereby dedicate a whole section to transmission lines.