A complete circuit,
no part of which was in contact with the magnet, was thus obtained.
He found that when the magnet and the external wire were rotated
together no current was produced; whereas, when either of them was
rotated and the other left at rest currents were evolved. He then
abandoned the axial wire, and allowed the magnet itself to take its
place; the result was the same.[2] It was the relative motion of
the magnet and the loop that was effectual in producing a current.
The lines of force have their roots in the magnet, and though they
may expand into infinite space, they eventually return to the magnet.
Now these lines may be intersected close to the magnet or at a
distance from it. Faraday finds distance to be perfectly immaterial
so long as the number of lines intersected is the same.
For example, when the loop connecting the equator and the pole of
his barmagnet performs one complete revolution round the magnet,
it is manifest that all the lines of force issuing from the magnet
are once intersected. Now it matters not whether the loop be ten feet
or ten inches in length, it matters not how it may be twisted and
contorted, it matters not how near to the magnet or how distant from
it the loop may be, one revolution always produces the same amount
of current electricity, because in all these cases all the lines of
force issuing from the magnet are once intersected and no more.
From the external portion of the circuit he passes in idea to the
internal, and follows the lines of force into the body of the magnet
itself.
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