Hello, I'm playing around with different high frequency, high voltage circuits and to connect everything together I am using this extra thermostat wire I have laying around, it is easy to use as it bends very nice, and I plainly have a ton of it. The circuit does not generate a ton of heat or anything but what I am noticing is that after I experiment with the device for some hours. When I go to remove the wire it is extremely brittle and just snaps. Anyone know what could cause copper to become brittle like that? Like I said, it goes on great, turns easy and is soft to begin with so im confused....any input appreciated.

 

As the copper heats and cools down repeatedly it becomes tempered. my parents had a piece of romex going to a pump next to a pond the wire developed so much resistance that added with the pump the AC drop down to 60 volts

 

How much current is going through the wire?
What is the wire size?

 

Are you familiar with the phenomenon of work hardening?

 

It depends on what you mean by high frequency and at what power. Skin Effect heating can easily harden copper.

https://www.nutsvolts.com/magazine/article/the_secret_life_of_a_wire
THE SECRET LIFE OF A WIRE