Practical Guide to Using Ohm's Law for Heating Copper Wire

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Discussion Overview

The discussion revolves around the practical application of Ohm's Law to heat copper wire for the purpose of removing construction adhesive from plastered walls. Participants explore various wire types and their properties, as well as alternative methods for achieving the necessary heat.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks to determine the voltage and amperage required to heat 10 or 12 gauge copper wire to several hundred degrees for adhesive removal.
  • Another participant suggests that copper is not suitable due to its high conductivity and weakness when heated, recommending Nichrome or Konstantin wires instead.
  • A participant mentions that a couple of amps should suffice to heat the wire enough to melt glue, proposing a resistance of about 2 or 3 ohms per meter for the wire.
  • Concerns are raised about the safety of using heated wire, with warnings about burns and fire hazards.
  • One participant expresses intent to test various braided wires before considering Nichrome or Konstantin wires.
  • Another participant suggests using a steamer, but this is dismissed as insufficient for the required temperature.
  • A participant notes that the internal resistance of the power supply could lead to most voltage being dropped across it rather than the wire, complicating the heating process.
  • There is mention of testing wire resistance with an Ohmmeter to find suitable options.
  • One participant shares an experience with iron wire being a good conductor and notes that even Nichrome used in appliances may not have the right resistance for this application.
  • Discussion includes a reference to abrasive wire used for cutting, which is presented as an alternative method.

Areas of Agreement / Disagreement

Participants express differing opinions on the suitability of copper wire versus resistance wire like Nichrome or Konstantin. There is no consensus on the best approach, and multiple competing views remain regarding the type of wire and methods to achieve the desired heating effect.

Contextual Notes

Participants acknowledge various limitations, including the need for specific resistance values in wires and the potential hazards associated with heating elements. The discussion does not resolve the technical challenges presented.

askme233
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OK,

Strange question, but I have a very practical, if simple, need to apply the Law.

I need to heat a copper wire to several hundred degrees and I am trying to figure out a rough voltage and amperage to push through it. I am staring at

http://www.epanorama.net/documents/wiring/wire_resistance.html

trying to figure out what I need to push through 10 or 12 gauge 2m copper wire to get the heat I need.

For an explanation of what I am trying to do, see below:
______________________
stupid previous owner used construction adhesive to glue paneling to 200 year old hand plastered walls. Ripping to panels off simply rips the plaster off of the wall. The adhesive fails rapidly under moderate heat from a torch, but I can't get the torch behind the panels. Bad alternative plan consists of a using a car battery charger to push 6-12 A at 12V until the copper is nice and hot and then pull the wire down behind the panels to cut through the adhesive.
_______________________

The obvious approach is to experiment and see what happens, but I figured I should be applying a very basic scenario of Ohms law, and thought you guys (gals?) might be able to help me out under the assumption I fail.

suggestions appreciated
 
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Copper would be a poor choice here because
A) it is a very good conductor and requires a lot of current to make it get hot.
B) when it is hot is is very weak and would break easily.

It would be better to look at Nichrome or Konstantin wires. There are used to make heating elements for toasters, room heaters etc.
You would need about 16 gauge wire for strength and some way to hold it when it is hot.
This has quite a lot of resistance per meter and stays strong even when it is hot.

You don't need it to be red hot and a couple of amps should be sufficient to make it hot enough to melt some glue.
There are different grades of resistance wire and they always show the resistance per meter on the roll. You might be looking for something like 2 or 3 ohms per meter. This would give you 3 amps or 2 amps from 12 volts across a 2 meter length of wire.

Just to remind you, this is a hot wire and it can burn your fingers or maybe start a fire if you are not careful.

It can also cut polystyrene foam.
 
VK6kro

Thanks for the feedback. While I may not have those specific types of wire around the house, your points make a lot of sense: use something not meant to conduct well. I will try some various braided wires first and if they don't work, start looking around for the ones you mention.

The health warnings are both obvious and appreciated. Never hurts to point those things out and might hurt if you don't.

ASK
 
This sounds like a difficult problem Have you tried a steamer ?
 
Thanks but a steamer wouldn't get anywhere near the temp needed for the adhesive to fall apart. I also tried using a torch to heat the outside of the paneling and just ended up witha lot of scorched paneling.

If the wire trick doesn't work, it is off to find way to hook up a big propane tank to a torch attachment.
 
Any good electrical supply store should carry Nichrome wire.
They may call it resistance wire.

But you would need to look for the resistance per meter to be about right.
 
To elaborate, the problem with using a copper wire is this: your supply circuit has some internal resistance, likely around 10 ohms. If your load (the wire) has about 0.01 ohms resistance, almost all the voltage will appear across your power supply's internal components, and the power supply itself will get much hotter than your wire.
 
ah yes, why didn't I think of that? I have an Ohmmeter in front of me. I will just test for the highest resistance.

ASK
 
Most wires you will probably find will have a lot less resistance than what you need.
I tested a length of Iron wire as sold in hardware stores and it was a very good conductor.

Unfortunately, even the type of Nichrome used in domestic 110 volt appliances has too much resistance for your application, so you would probably have to get the right stuff at a suitable store.

The health warning. I am conscious of the number of "views" on the main page and sometimes throw in something like that, more for general consumption than for the person I am addressing.

I have seen some abrasive wire used for cutting. It works like a saw and has a handle at each end.
Like this:
http://www.survival-gear.com/wire-camping-saw.htm
 
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