I set down a magnet on my table. When I picked it up, a bunch of jumper wires came with it...Strange, I thought.
Turns out about half the assorted ones I had, displayed this mysterious effect....the wires even look like copper, but apparently are steel coated copper, or have ferrous deposits in the mix (maybe they just melt a bunch of different scrap metals together).
They snapped strongly to the magnet so it's more than a little iron residue. The good jumpers weren't even slightly attracted to the magnet. I want a refund!! Calling China to speak with Happy Luck Treasure.
I've noticed this with some resistor leads & headers, but never jumper wires.
The stripped wire pic has both ends cut off...so it is wire only...looks like nice shiny pure copper---not!