question regarding the boundary behavior of electric current

Apr 10, 2007 2 Replies

Hi,



I have a cable and I send electric current through it. I want to know the moment when the current has arrived at the other end of the cable.



Can I visualize this moment by using an oscilloscope ?



If the answer is yes, I have another question for a more complex experiment.



I have a very simple network with 2 nodes (A and B). There are 2 cables which are connecting these nodes. The cables have different lengths L1 and L2. Assume that L1 is shorter than L2.


I have draw a small picture here:


--A*-------L1---------*B-- | | | | |______L2_____|


I apply electric power to this device. Because the cables have lengths greater than zero I assume that it will take a while until the current traverse the path from A to B.



More than that, in node A, the current is split in 2, because there are 2 cables linking A with B. Because one of the cables is shorter I assume that "a part" of the current arrives earlier (denote this by moment M1) than the other "part" because it has to traverse a shorter path. Am I correct ?



The other "part" of the current which has traversed cable L2 will arrive later in B. Lets denote this by moment M2.



Can I measure these 2 moments by using an oscilloscope? Or what other options for measurement I have ?



Are there some fluctuations of the electric current at moments M1 and M2 ?



Are there high precision oscilloscopes for this experiment? Or should I use very very long cables?



I'm not interested what happens after those moments.


Thanks, Laura



Sure, as long as your scope is good enough.

The speed of light (in air/vaccum) is 1 ft per ns. How long are your cables and how good is your scope?

google for >transmission line<

These are my opinions, not necessarily my employer's. I hate spam.

Laura, You are describing the operation of a time domain reflectometer. Ray

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