Siggy wrote:
A while back there was a discussion about why wall wart transformers that
were not under load would draw no current. Anyone recall that thread? As I
recall there were some references to the induced currents created by
collapsing magnetic fields etc.

Anyway, I'm trying to either prove or disprove the statement that unplugging
wall warts when not actually using them to power or re-charge your device
will save electricity. My recollection is that it doesn't matter. Right or
wrong?


True. Any transformer has slight losses, even when idling. Just FEEL a
'wall-wart' ... they get warm, even when NOT under significnt load. That
heat comes from resistive losses in the wire and magnetic losses in the
core. Even when NOT under external load, there are short-term internal
current flows in the coils (or there would be NO magnetic field).
Current in a wire is always a resistive LOSS, no matter which way it
flows. For a well designed transformer, those losses are slight, but
never zero. It's doubtful that you'd ever SEE a difference in your
electric bill from letting ONE idle, however.

Dan Mitchell
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