Hi all.

I have yet to understand what's so great about double-wound coils.? As far as I can see, they are no different from ordinarily wound coils. Take, for instance, the experiment described at

http://www.tesla-coil-builder.com/bifilar_electromagnet.htm

It's no hassle to set up this simple experiment, so I gave it a try.? I didn't observe any "enhanced magnetising force" around the bifilar. I even made a test with two cascaded coils to ensure that the core wasn't in saturation.? What I did notice is that using paper clips to measure magnetic field strength is rather inaccurate.? Not only is the measurement taken in large chunky steps, but it also ignores the remanence of the steel in the clips. If the last clip to be added is already magnetised then this magnetism can add to, or work against, the main field.

Maybe someone can repeat this test with a hall sensor and give us a clearer picture.? Failing that, I would simply recommend to our group members to steer clear of bifilar coils. There is simply too much bull, out there, wasting our time. Just think, if bifilars were really so great, then all the transformers being sold worldwide would be simply wound up in this manner!

Regards
Joseph

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