The short length and very few coils on most cables isn't going to cause any harm.
Now, in theory, if you have a 100' tightly rolled cable, and only use a few feet of each end to connect things together because it's the only cable you have, then plop it on top of a fluorescent light with a magnetic ballast or over a server power supply and/or fan array (fans all use magnetic force to spin them), there may be enough of a moving magnetic field to induce a current.
Depending on the equipment, it will range from damaging the network port and making it permanently inoperable or it will just cause massive amounts of interference that causes too many CRC errors and/or the ports will not negotiate a connection and if they do, it'll be like 10 Half.
I've actually experienced the latter at customer sites when I was working consulting.
I would put in a proper length cable, routed away from the power supplies, fans, and lights, and the problem would be resolved.
Tell the customer it was a bad cable, keep the 100' for where it's needed.
Same problem can happen when cables are straight but bundled in parallel with AC cables.
They can induce enough of a current to cause interference.
Move the cable at least 12" away from the wiring, and all is good.
If you must cross over AC wiring, you must do it perpendicular to it. That way the twisted pairs will cancel the noise.
Sounds interesting but its mostly theory . And there was only like 3-10 meters of cable and not so tightly rolled , and its Ethernet cable , its designed not to induce current. Now im getting out of my knowledge zone LOL.
Just show me some video, or text with proof that its possible with ethernet cable and i will reconsider
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