[Terr_]

That seems pretty excessive, IIRC if there's not a really long linear length of wire involved (e.g. power lines) then things are probably fine.

[lgats]

This would better prepare them for an Air Burst https://en.wikipedia.org/wiki/Air_burst

[cout]

Why would long lengths of coiled wire not be affected?

[quesera]

For the same reason that a crumpled up ball of wire is a bad antenna.

To induce an appreciable current, the magnetic field has to act on a wave-compatible portion of the conductor. The length and alignment of the wire has to resonate with the direction and length of the wave.