On 24/02/18 11:44, Brian Gaff wrote:
One might imagine the
other cables like mains
Mains only causes a problem if the wiring is faulty. If the wiring is
intact, the loop is formed between the live and neutral in the same
cable, so has a very small area. In a ring main, if one ring is broken
on just one conductor, or there is a high resistance joint on one
conductor, the whole ring can become the loop, with something of the
order of half the total current.
It is also possible that modern aids filter the the 50Hz out, so the out
of balance current may have to be harmonics (form rectifiers, etc.)
The flat above me seems to have this problem, but trying to explain it
to the owner would be too technical.
There are ways I imagine you could connect lighting switches such that
large loops were formed.
Obviously such problems will also exacerbate hum loops in audio systems.