Smithsonian Institution - United States National Museum - Bulletin 240: Contributions From the Museum of History and Technology; Papers 34-44 on Science and TechnologyMuseum of History and Technology (U.S.)
History
Smithsonian Institution - United States National Museum - Bulletin 240: Contributions From the Museum of History and Technology; Papers 34-44 on Science and Technology
Museum of History and Technology (U.S.)
Science -- History; Technology -- History
Poggendorf's own account of his work finally appeared as a very long
article in the journal known as "Oken's Isis."[28] The editorial
controversies mentioned earlier may have occasioned this use of a
periodical of such minor status in the fields of physics and chemistry.
The source of Poggendorf's vision of the multiplier principle was a
little different from Schweigger's inspiration. Aiming at some detailed
analysis of Oersted's observation, Poggendorf ran the connecting wire of
his cell-circuit along a vertical line to just above or below the
pivot-point of the compass needle, then, after a right-angle bend,
horizontally above or below one of the poles of the needle. As he
studied the deflections produced for all four possible positions of such
a wire, with both cell polarities, he came to realize that if a
rectangular wire loop in a vertical plane enclosed a compass needle, all
parts of the horizontal sides of the loop would produce additive
deflections. By a separate experiment, he showed that the vertical sides
of the loop would also increase the deflections. He saw at the same time
that the effect of additional turns would be cumulative.
The multiple surrounding of the needle by a silk-covered wire, in a
plane perpendicular to the long axis of the needle, affords the
physicist a very simple and sensitive means of detecting the
slightest trace of galvanism, or of magnetism produced by it, so
that I have given the name of magnetic condenser to this
construction, though I attach no special value to this name ...
In analyzing the astonishingly increased power which the condenser
gives to the magnetic effect of a circuit, the first question that
arises is how the effect varies with the number of turns, whether it
increases indefinitely or reaches a maximum beyond which additional
turns have no effect. The answer to this first question is linked to
the solution of another, viz, whether the degrees deflection are a
direct expression of the measure of the magnetic force or not.
To instruct myself on this point I made use of three separate
circuits, each containing an 8-turn condenser, and put these as
close together as possible in the magnetic meridian ... with the
needle between the windings. Each single circuit ... gave a
deflection of 45° ... When two were connected the deflection was
60°, and when finally all three were put in magnetic operation, the
deflection grew to only 70°. It appears clearly from this that the
angle of deflection is not in a simple ratio with the magnetic force
acting on the needle....
Neither Poggendorf nor Schweigger seems to have ruled out, on logical
grounds alone, the possibility of deflections greater than 90°, with the
loop-plane in the magnetic meridian, though Poggendorf does add a vague
note that if the needle deflected too far it would encounter forces of
the opposing sign.
Public-domain text, read in full here on John Shaqi.
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