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

On 10 Apr 2007 12:11:07 -0700, "laura" <l...@gmail.com>
wrote:

>
>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 ?

Yes.
>
>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.

Yes - a signal in a wire (particular coax cable) travels at about 2/3
the speed of light.
>
>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 ?

Yes.
>
>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 ?

Yes, these time delays can be measured using an oscilloscope, provided
the scope has a sufficiently fast sweep rate.
>
>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?

The delay is about 1.5 nS per foot, so you don't need particularly
long cables to observe this.
>
>I'm not interested what happens after those moments.
>
>
>Thanks,
>Laura

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