# Can someone help me identify the wires?
**URL:** https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224
**Category:** Factual Questions
**Created:** [May 14, 2008, 12:44am UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224 "2008-05-14T00:44:25Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@wisernow](https://boards.straightdope.com/u/wisernow)
#### Post date: [May 14, 2008, 12:44am UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224/1 "2008-05-14T00:44:25Z")
I have an AC to DC converter that plugs on to a wall outlet and delivers 9V DC as the output. The connecter on the 9 volt end is the cylindrical type -something like the one on the far right in the picture under “Cylindrical Types” [here](http://en.wikipedia.org/wiki/DC_connector) - the one near the 9" marker on the scale.
By accident the pair of wires between the converter and the connector have been severed. I would like to connect them back and I don’t have a multimeter or continuity tester. I was wondering if it is possible to identify one of the wires as a positive or negative just by sight. The only difference in the two wires is that the insulation on one has whitish bands along its length. Is that some sort of an indicator of polarity?
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [May 14, 2008, 12:48am UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224/2 "2008-05-14T00:48:13Z")
By convention, the marked wire is the positive one (there are always exceptions, of course). But, it shouldn’t matter, assuming you have enough wire on either side of the break to make a splice–just match them up.
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### Author:  [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)
#### Post date: [May 14, 2008, 2:12am UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224/3 "2008-05-14T02:12:44Z")
Cut the red wire. Always cut the red wire.
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### Author:  [@moes\_lotion](https://boards.straightdope.com/u/moes_lotion)
#### Post date: [May 14, 2008, 5:38am UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224/4 "2008-05-14T05:38:27Z")
[QUOTE=Exapno Mapcase]
Cut the red wire. Always cut the red wire.
[/QUOTE]
**Unless…** there are two blue wires, then cut the other one!
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### Author:  [@Wheeljack](https://boards.straightdope.com/u/Wheeljack)
#### Post date: [May 14, 2008, 6:37am UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224/5 "2008-05-14T06:37:32Z")
[QUOTE=wisernow]
Is that some sort of an indicator of polarity?
[/QUOTE]
Yes, it is.
What I don’t understand is if you’ve got a white marker running down the wire, why can’t you just connect both sections of wire that have a white marker, and both sections that don’t? There must be something I’m missing here.
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### Author:  [@wisernow](https://boards.straightdope.com/u/wisernow)
#### Post date: [May 14, 2008, 12:23pm UTC](https://boards.straightdope.com/t/can-someone-help-me-identify-the-wires/449224/6 "2008-05-14T12:23:42Z")
[QUOTE=Wheeljack]
Yes, it is.
There must be something I’m missing here.
[/QUOTE]
You’re right. But it’s not you. It’s me. I am missing my brain somewhere. :smack:
:rolleyes: to myself.