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I was working on an electronics project today and tried powering it with a battery but nothing happened and the battery was new. I eventually used my multimeter and read no voltage at the output of the wires and after measuring the resistance it was reading 0 ohms.

I got another brand new wire and it indeed measured a resistance. I think the old wire is somehow broken but I'm not sure if that's even possible as I've never heard of anything such as this.

Do wires go bad over time? I was under the assumption that wires will keep being conductive forever? If so, what could've caused this and what is actually making the wire behave this way? Thank you.

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    \$\begingroup\$ Wires can break or fail or become corroded/oxidized. But 0 Ohms means you have a good connection not a bad connection. \$\endgroup\$
    – user57037
    Commented Feb 8, 2021 at 9:09
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    \$\begingroup\$ Generally its the connectors and/or solder joints at the end of the wire that's the usual culprits, more so than the wire itself. Why would 0 ohms be bad? That's the expected resistance on a good copper wire with your average multimeter. Isn't it rather your multimeter telling you "infinite resistance" (no connection) rather than 0 ohm? \$\endgroup\$
    – Lundin
    Commented Feb 8, 2021 at 9:36
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    \$\begingroup\$ @mkeith Unless the reading was 0 L instead of 0 ohms. \$\endgroup\$
    – Criggie
    Commented Feb 8, 2021 at 23:17
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    \$\begingroup\$ @Criggie yes I think that is likely the explanation. \$\endgroup\$
    – user57037
    Commented Feb 8, 2021 at 23:36
  • \$\begingroup\$ Do you know for sure that that wire worked before, and it wasn't an enameled wire? \$\endgroup\$
    – Nat
    Commented Feb 9, 2021 at 6:37

5 Answers 5

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You may have developed an oxide layer or have an insulating contaminant over the exposed parts of the wire that you were using. Try cutting and stripping both ends and test again.

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Wires can break if they are moved regularly. Any metal item can suffer from metal fatigue if it is bent repeatedly, and copper wire is no different.

In places where vibration or repeated bending is an issue, stranded wires are used in place of solid ones, with finer strands used for more strenuous applications. Even a stranded wire can fatigue and break.

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    \$\begingroup\$ To add to this, a break in a wire from metal fatigue tends to result in an intermittent connection, because the insulation holds the now-disconnected ends close together, and wiggling the cable can push the ends back together. This makes it hard to spot. For an even more obscure fault, I once had a guitar cable which fatigued in some bizarre way which turned it into a low-pass filter - that was even harder to track down, because twanging a low E string to check the signal path was working! \$\endgroup\$
    – Graham
    Commented Feb 9, 2021 at 11:08
  • \$\begingroup\$ +1 but insulation can crack due to material fatigue and friction too. And it can age out faster than metal. Probably not an issue to the specific case, but worth noting for the general "Do wires go bad?". \$\endgroup\$
    – Mołot
    Commented Feb 9, 2021 at 12:01
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Its pretty unlikely, but it is possible to get two ends of different wires.

Specially if you're working with a bundle or loom of wires, two disjoint ends won't carry electricity at all. So do check your assumptions, like

is there more than one wire of this colour in the loom ?

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Yup.

melted extension cord

For instance, most wires go bad when you push too much current through them. Perhaps there was a defect in yours. Stranded wire of poor quality for instance could have a section with weak or missing strands. Then "too much" current might be far less than you expected.

And if the current is low enough ad wire gague small enough, (and you're unlucky enough) then it might just be able to break the circuit inside the insulation without being externally noticeable, especially if the insulation is already black/dark brown or just dirty.

Hopefully it's just oxidation on one of the ends and can easily be cleaned off or cut and re-stripped.

If you try that and it doesn't work and you have to replace the cable anyway and you're curious, do a dissection. Strip the entire length. You will eventually see the problem. Share a photo when you figure it out.

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    \$\begingroup\$ What a nice image of a cable fondue! Tasty. But -- what are these fascinating hair/crystal like spikes growing out the drum!? \$\endgroup\$
    – Peter - Reinstate Monica
    Commented Feb 9, 2021 at 11:33
  • \$\begingroup\$ Oh, another thing: The wire is probably just fine. \$\endgroup\$
    – Peter - Reinstate Monica
    Commented Feb 9, 2021 at 11:36
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    \$\begingroup\$ Looks like tinsel for a Christmas tree. \$\endgroup\$
    – IconDaemon
    Commented Feb 9, 2021 at 13:40
  • \$\begingroup\$ I was once at a concert that went pitch black, someone had forgotten to unwind the spool. Always unwind your spools fully. \$\endgroup\$
    – Tschallacka
    Commented Feb 9, 2021 at 14:32
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    \$\begingroup\$ someone's EV charger was too far from an outlet so they grabbed a chincey harbor freight extension cord..... \$\endgroup\$
    – Billy left SE for Codidact
    Commented Feb 9, 2021 at 21:05
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We bought a batch of ribbon-cable style patch leads with individual 0.1" pin sockets on each end, and they must have been made with incompatible plastic and wire, because all the brown leads and some other colours just broke when pulled on or when attempting to strip them leaving black and white dust in the insulation where the wire should have been. They often worked at first then died open circuit.

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