Talk:Speed of electricity

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Some references on Hertz

After discovering electromagnetic waves, Hertz studied the question whether the electromagnetic waves ("space waves") travel at the same speed as the disturbance in the wire ("wire waves"). He initially found a discrepancy, but the more controlled experiments by Edouard Sarasin and Lucien de la Rive in 1893 established that both travel at same speed. Some sources discussing this:

Yeang, Chen-Pang (2024-01-30). "Electromagnetism and Electrodynamics in the 19th Century". Oxford Research Encyclopedia of Physics. Oxford University Press. doi:10.1093/acrefore/9780190871994.013.131. ISBN 978-0-19-087199-4. Retrieved 2025-12-19.
Darrigol, Olivier (2003). Electrodynamics from Ampère to Einstein. Oxford University Press. pp. 247–251. ISBN 978-0-19-850593-8.
Buchwald, Jed; Yeang, Chen-Pang; Stemeroff, Noah; Barton, Jenifer; Harrington, Quinn (2021). "What Heinrich Hertz discovered about electric waves in 1887–1888". Archive for History of Exact Sciences. 75 (2): 125–171. doi:10.1007/s00407-020-00260-1. ISSN 0003-9519.

Jähmefyysikko (talk) 09:55, 19 December 2025 (UTC)

Done thanks I added a paragraph to History, please review. Johnjbarton (talk) 19:48, 12 January 2026 (UTC)

Permittivity

The article indicates that: Usually in good conductors e.g. copper, silver, gold, $\varepsilon _{r}=1$ . That seems to disagree with this one, which indicates large and imaginary. Gah4 (talk) 21:53, 22 December 2025 (UTC)

That passage: "In the low frequency regime, the effective relative permittivity...". effective relative permittivity is a single complex number that combines permittivity with conductivity. It is not the same as relative permittivity.

Looking at the reference there^[1], near equation 4.1 he defines effective permittivity as

{\tilde {\epsilon }}=\epsilon +i{\frac {\sigma }{\omega }}

and he gives

\epsilon \approx \epsilon _{0}

which is what this article gives. Constant314 (talk) 22:19, 22 December 2025 (UTC)

References

[1]
Lourtioz, J.-M.; et al. (2005). Photonic Crystals: Towards Nanoscale Photonic Devices. Springer. pp. 121–122. ISBN 978-3-540-24431-8. equation (4.6), page 121

Talk:Speed of electricity

Some references on Hertz

Permittivity

Direct current electricity means the current in the conductor is in a constant E field. This is not correct.

In general, electrons propagate randomly in a conductor at the Fermi velocity, and the Fermi sphere.

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