Re: BOUSSOLE ? BIO ?

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

I was wrong, "biot" was a unit of electric current (not the unit
of B or H). It was a current needed (in each of the two very
long parallel wires) to create a force of 1 dyne per centimeter
when the distance between the wires is 1 cm. It was named
after Biot, a contemporary of Ampere. Biot was the first to
discover (by using the oscillating compass needle method)
that the magnetic "field strength" near a long wire is directly
proportional to the current and inversely proportional to the
distance. He was also very productive in optics. But I less
certain that he (and his student Savart) were the first to
formulate the law associated with their names. Perhaps they
validated experimentally what was suggested by Ampere.
Perhaps somebody who knows will comment.
Ludwik Kowalski

"Polvani, Donald G." wrote:

> The oersted is the old Gaussian unit for H.  It was adopted in 1934 by the
> International Union of Pure and Applied Physics who took the view that B and
> H in free space are fundamentally different even if their ratio mu0 is taken
> as unity.  B was measured in gauss in the same units (from W.S. Scott, "The
> Physics of Electricity and Magnetism", second edition, 1977, p386)