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Say I am sending a pulse down a five foot wire. If I want the pulse to not reach the end of the wire, but instead reflect at say the two foot mark, how could I achieve this without physically touching the wire?

I thought to use magnets, but I'm not sure if I'm on the right track.

Any help is appreciated.

Thanks!

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  • $\begingroup$ And by "not touching" you mean what? The easiest way is a wire cutter. You wouldn't be touching the wire, but the wire cutter would. After that we can go with an acetylene torch. How about a laser? $\endgroup$
    – CuriousOne
    Commented Jan 5, 2015 at 6:07
  • $\begingroup$ @CuriousOne haha yes I guess that answers the question. Although I meant without you or any tools making contact, for example, placing it under a magnetic field (not saying this would work). $\endgroup$
    – LimitedBacon
    Commented Jan 5, 2015 at 6:09
  • $\begingroup$ You are not by chance in a submarine, looking at a thick underwater cable? :) $\endgroup$
    – mvw
    Commented Jan 5, 2015 at 6:11
  • $\begingroup$ @mvw actually trying to sneakily take out my neighbor's cable $\endgroup$
    – LimitedBacon
    Commented Jan 5, 2015 at 6:12

2 Answers 2

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If, as your comment indicates, you're talking about a coaxial cable such as 75\$\Omega\$ RG-59, it's virtually impossible realistically to affect it as you suggest (the coax keeps signals in and interference out). Well, you could heat it (perhaps with an induction heater) until the insulation vaporizes and the copper melts which technically would not be touching it, but I don't think that's what you want.

If a straight pin were to find its way between the outer shield and the inner conductor such that the two were shorted together, it would accomplish what you say you want. If it broke off flush, it could be fairly hard to detect, though a TDR (time domain reflectometer) would point to the general location within maybe 50cm. (RG-59 Image from Wikipedia commons)

http://upload.wikimedia.org/wikipedia/commons/7/73/RG-59.jpg

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  • $\begingroup$ Haha it was a joke, but I appreciate the great detail you went into. Maybe it can be put to use in future ventures! It's actually just a hypothetical scenario. $\endgroup$
    – LimitedBacon
    Commented Jan 5, 2015 at 7:02
  • $\begingroup$ There are some interesting things that can be done with superconductors and heat or magnetic fields, (also UV light). $\endgroup$
    – Spehro 'speff' Pefhany
    Commented Jan 5, 2015 at 7:03
  • $\begingroup$ I'll look into that! I appreciate the responses $\endgroup$
    – LimitedBacon
    Commented Jan 5, 2015 at 7:04
  • $\begingroup$ 50cm? TDR can do waaaaaaay better than that. $\endgroup$
    – DanielSank
    Commented Jan 5, 2015 at 7:48
  • $\begingroup$ @DanielSank Sure, I've seen millimeters resolution, but prolly a cable guy would have something a lot cruder. $\endgroup$
    – Spehro 'speff' Pefhany
    Commented Jan 5, 2015 at 8:18
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If you can make two kinds of wires a 3 foot one and a 2 foot one, then you can try attaching them, and make sure the impedence is mismatched. If you can adjust the temperature at one end severly and make your wire(s) out of something that has a temperature induced conductivity change that might get a nice effect.

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    $\begingroup$ if the entire wire is the same kind? (creative solution though) $\endgroup$
    – LimitedBacon
    Commented Jan 5, 2015 at 6:10
  • $\begingroup$ Maybe make it something that gets destroyed (it is a pulse after all, not even a wave), I imagined a wire made out of ice at first, and imagined having super cool ice at one end and barely frozen at the other, maybe it will just fail spectacularly at some point in between. You can try to get a dispersion effect too send waves each pulse-like but each centered at a different frequency and each timed so that they all reach the same unfortunate point at the same time. And maybe it is a superconductor but the current when they all collide is just too much and it switches to a nonsuperconductor. $\endgroup$
    – Timaeus
    Commented Jan 5, 2015 at 6:19

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