The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1891-05-15
ELECTRIC DYNAMOS,
MACHINERY THAT CAUSES THE Al
TERNATING CURRENT.


Wheel and the Present Powerful Elec
tro-Magnets-Diferen in the TIVE
Currents-The Machine.
The first dynamo electric machine
ever constructed was made by Faraday
This great physicist, the prince of ex
perimenters, as he has been called, dis
covered that when disc or fat plate Of
copper was made to rotate between the
poles of a powerful magnet currents were
produced in the plate from the center out
ward. By making wire touch the re.
volving plate with one of its ends and
bringing the other one in contact with
the rim he found that a current of cleo.
tricity passed along the wire, and could
be made to indicate its existence by de-
fecting the needle of a galvanometer,
decomposing a chemical solution, or by
any of the well known effects produced
by electricity in motion.
Faraday saw the Importance of this
discovery and the great uses in the way
of practical application to which it
might be put, but he did not himself
stay to develop it; he left that to others,
and with it the wealth which might
thus be acquired, and himself went on
to investigate other obscure and little
known phenomena connected with phys.
les and electricity, regarding this as his
proper work, and exhibiting in his con-
duct the true scientific spirit. When
many years afterward he went to see
the first application of this discovery Of
his to the production of the illumina-
ton of the North Foreland lighthouse,
he said, after looking at the large mag
neto-electr.c machines there, Il gave it
to you an infant; you have made it a
giant"
Dynamo and magnetic electric ma
chimes consist essentially of coil of wire
1.-THE armature," as it is called-rotat-
ing between the poles of large mag
net, the poles being bent round SO as to
each other and have the arma-
ture between them. This magnet may
be either permanent magnet of hard
steel, or an electromagnetic consisting of
wire coiled round a soft iron core, a cur
rent Of electricity being made to circle
round the wire coil rand thus magnetic
ing the iron core while it lasts. 1t is the
latter arrangement which is almost uni
used now, though the magnetic
machines with permanent magnets were
the earliest form.
THE ELECTRO-MAGNET.
A magnet produces an influence in the
around it, and this sur
neighborhood is known as the
field of force" of the magnet e., the
sphere in which its influence can be felt.
A magnetic needle or bit of iron filing
placed in this field sets itself to point
dong the Lines of force" of the field
hat Is, the lines along which the mag
letic force acts, and which form curves
ound the magnet, running out, as it
we're, from pole to pole, and curving
ound to the other. Any one may see
he form of these lines of force for him.
elf by placing bar magnet underneath
! sheet Of paper and then sprinkling
ilings on the paper.
On tapping this the filings will set
themselves along the lines of force in
'eautiful regular curves Here the small
fragments Of iron are themselves made
magnet while under the influence of the |
'owerful magnet in whose field" they
re, and therefore place themselves
enSthwise along the lines of force-that |
J, along the line of action Of the result !
MT magnetic force at the place where
ach one is.
When a coil Of wire or armature is
1ade TO revolve rapidly in the strong
ED of force which occupies the space
etween the poles of powerful electro
lagnet currents are produced in the
OIL. These currents alter their direc-
on through the coil every time the lat
n changes its position with reference
the poles Of the magnet. The side of
ne coil, which was opposite the north
ole, Is after half revolution opposite
he south pole, and the influence of the
outh pole tends to produce an opposite
lrrent to that of the north pole. Here
e have an alternate current" dynamt
lachine.
PROCESSES OF USING THE CURRENT.
As the coil or armature rotates with
-eat speed-sone hundreds of revolu-
ons per minute-these currents, in al
rnatng directions. succeed each other
cry rapidly, and if an electric arc lamp
placed on the circuit it will be lit ND.
this case II is not necessary that the
lrrent be sent round the circuit in one
rectlon only, but although the termi-
ais of the lamp are constantly changing
eIr polarity-that is, the north pole
here the current enters the next in
ant becomes the south pole where the
lrrent leaves-yet, as this occurs MANY
mes IN one second, the effect produced
the same as if the current was in one
inform direction.
The lamp has no time TO cool; it does
1t go out before the oppositely directed
TRENT passes through it and produces
e same effect as the previous one. No I
ckerlng Is observable. The impression ,
oduced by the glowing carbon on the |
imam eye is retained by the retina for
tar longer period than the duration of
e surge OF electricity through the
mp, ana Is not gone before the effect
oouced by the succeeding opposite
ave makes Its impression on our nerves.
In continuous current DYNAMO. s
nch Is necessary for some purposes,
en- rs electro-plating, where the effect /
sired could not be produced if the d. l
,t!on Of the current was continually
erlng, the electric current is made 70
s. always one way round the external
cult. This result is got by using the
,enlous device OF a commutator. !.
Iich automatically defects the current !
as ALWAYS 10 send II in an ucyarrinn !