Field geom. figure 8 coil

It will make two adjacent loops with opposite directions of current flow, of course. You can work out the resulting magnetic field strength for yourself/

Chris

The radiated field is that of a dipole, and decreases rapidly with distance - IIRR as the fourth power of distance along the long axis of the 8 and even faster as you move away fro that axis.

-- Bill Sloman, Nijmegen

Not a dipole--the dipole moment cancels if the two loops are the same size. It's a quadrupole.

Cheers

Phil Hobbs

Third power.

Isn't the close-in field sort of toroidal?

John

Yes, although that's also true of a simple current loop. Putting two coils next to each other doesn't produce a very high coefficient of coupling, so it doesn't look much like a toroid toroid. The two opposing dipoles cancel out in the far field--all that's left is the quadrupole, which is two equal and opposite dipoles offset from each other.

Cheers

Phil Hobbs

r.

Maybe there are other, higher-order corrections; the figure-eight configuration doesn't have the exact symmetries of a pure quadrupole; that would require two figure-eights at right angles. The far-field will be dominated by quadrupole, but one cannot rule out some octopole or higher terms as small corrections.