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Veritasium "How Electricity Actually Works"
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PlainName:
For the sake of argument I went with 60pF. Derek's result I've attached along with my conservative (that is, relatively slow rise time) simulation. They look completely different, and I'm not convinced that splitting the 1 cap into however many your simulator can put up with will change things significantly. Specifically, the simulation shows a peak of close to the input level and then dies off very quickly, even on this much shorter timescale than the real thing.
SandyCox:

--- Quote from: electrodacus on May 16, 2022, 02:07:25 am ---
--- Quote from: dunkemhigh on May 16, 2022, 01:13:42 am ---
Doesn't matter if it's distributed - the entire thing has a very very short time constant. All you're saying is that if you imagine it comprised 100 smaller capacitors, each will be 2.1ff (i.e. 2.1pf/100).


--- End quote ---

Ues this calculator https://www.emisoftware.com/calculator/wire-pair-capacitance/
You can use 12mm wire radius 1m separation and 10m length and you will get 62pF total
I also checked with 1mm radius for fire and got about 40pf so I used 42pf in my simulation just to be conservative.

--- End quote ---
A lossless transmission line looks like a resistor at its input, not a capacitor. Please read Haus and Melcher or any other good book.
electrodacus:

--- Quote from: dunkemhigh on May 16, 2022, 09:12:08 am ---For the sake of argument I went with 60pF. Derek's result I've attached along with my conservative (that is, relatively slow rise time) simulation. They look completely different, and I'm not convinced that splitting the 1 cap into however many your simulator can put up with will change things significantly. Specifically, the simulation shows a peak of close to the input level and then dies off very quickly, even on this much shorter timescale than the real thing.

--- End quote ---

It makes a big difference when you split the capacitance and also inductance.
I guess you did not see my spice simulation that I posted earlier in the thread.
So here it is again.  Keep in mind I simulated only half the circuit the other side of the resistor is directly connected to source negative not through another transmission line and I did not add the influence of oscilloscope probes.
The important part is that shape is exactly the same with a slow rise and then a flat response until about 65ns



 
electrodacus:

--- Quote from: SandyCox on May 16, 2022, 12:15:32 pm ---
A lossless transmission line looks like a resistor at its input, not a capacitor. Please read Haus and Melcher or any other good book.

--- End quote ---

This is a real line and during transient the inductance and capacitance of the line play an important role as see from both experimental result and simulation.
During DC after the transient effect is gone it will be just a resistive line.
SandyCox:
Please read the book.

The experimental line will be close to a lossless line. The theory for lossy lines has also been worked out. Just read and you will learn a lot!

You are openly displaying your own ignorance.
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