Speed of Current in a coaxial cable

Thread starter Kyuubi
Start date Dec 14, 2022
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Cable Coaxial Coaxial cable Current Speed

AI Thread Summary

The discussion focuses on calculating the speed of current in a coaxial cable using its inductance and capacitance per unit length. It notes that multiplying these two values yields the speed of light, indicating a relationship between electrical properties and wave speed. The conversation suggests that similar principles used to determine wave speed in a string, based on tension and density, could be applied to coaxial cables. Participants are encouraged to explore analogous equations that incorporate capacitance and inductance for modeling wave behavior in coaxial systems. Understanding these relationships is essential for analyzing wave propagation in electrical cables.

Dec 14, 2022

Kyuubi

Homework Statement: Calculate the inductance and capacitance per unit length of a long coaxial cable, and show that the current, or equivalently charge, wave has speed v =1/√(µ0ϵ0) = c which is the speed of light.

Relevant Equations: Maxwell's equation in a vacuum.
Excuse me for not writing them, I'm not familiar with latex and I think I'll only need a conceptual answer. They should be in the photo though.

I've found the inductance and capacitance per unit length in a long coaxial cable. I even clearly see that if I multiply the two, I can get the speed of light. How do I begin to find the current wave and its speed though?

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Dec 14, 2022

haruspex

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Could you figure out the wave speed in a string of given tension and density? Maybe you could then use the same approach to model a wave in coax and find analogous equations using capacitance and inductance.

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