The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1891-04-09
A Very Simple Explanation Given Of
the Action Of Alternating
Currents.
The Firet Dynamo Electric Machine
Ever Constructed Was Made
by Faraday.
4 oil Of Wire Rotating Between tho
Poles of q Large Magnet IL an
Essential.

The hrHt dynamo-olectrtc mach1ne eVel
constructed was that made by Faraday,
This great physicist, the prince OF expert
mentors, az he has been called, discovered
that when a disk or fiat plate Of copper was
made to rotate between the poles of a pow.
erful magnet, currents were produced IN
the plate from the center outward, says
knowledge. BY making a wire touch
the revolving plate with one OF
its ends and bringing the other
ona in contact with the rim he
found hat n current of electricity passed
along the wire and could be made to ind
cate it's existence by DETECTING the needle
OF a galvanometer, ~decomposing a chemi-
cal solution. or by any Of the ~well-known
effects produced by electricity in motion.
Faraday saw the Importance of this dis
covery 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 in
investigate other obscure and little-known
phenomena connected with physics and
electricity. regarding this as his proper
work, and exhibiting in his conduct the
slue scientific spirit. When, many years
aftel ward, he went to see the first applica-
ton of this discovery of his to the produc-
ton of the illumination of the North Fore
land lighthouse, he said, after looking at
the large magneto-electric machines there,
II gave 1t to you an infant; you have made
it a giant"
Dynamo and magnetic electric machines
consist essentially of a coil of wire-"the
armuture," as il is collaborating be-
tween the poles of a large magnet, the
vno1ao haivn hnvt wound II IN n q IN pnrrnnI
each other and have the armature between
them. This magnet may be either a per-
manent magnet of hard steel, or an electro
magnet consisting of wire coiled round a
soft iron core, a current of electricity be-
ing made to circle round the wire coil, and
lasts. 1t is the latter arrangement which is
almost universally used now. though the
magnetic machines with permanent mag
nets were the earliest form.
A magnet produces an influence in the
neighborhood around it, and this surround
ing neighborhood is known as the field of
force" of the magnet; j. e., the sphere in
which its influence can be felt. A magnet
ic needle or bit of iron-flling placed in the
field sets itself TO point along the Zines of
force'' of the field; that is. the lines along
which the magnetic force acts, and which
forms curves around the magnet, running
out, as it were, from pole to pole, and curv-
AhA 1ouAlo w VAN oShSAs 1hy OAo AAA0y .
the form of these lines of force for lin
self by placing a bar-magnet underneath a
sheet of paper, and then %sprinkling ron
filings on the paper.
On tapping this the filings will set them
selves along the lines of force in beautiful
regular curves. Here the small fragments
of iron are themselves made magnets while
under the influence of the powerful magnet
in whose field" they are, and therefore
place themselves lengthways along the lines
of force, that is, along the line of action of
the resultant magnetic force at the place
where each one is.
When a coil of wire. or immature, is made
to revolve rapidly in the strong field of
force which occupies the space between the
poles of a powerful eleotro-magnet currents
are produced in the coil. These currents
alter their direction through the coil every
the latter changes its position with
reference to the poles of the magnet. The
side of the coil which was opposite the
north pole is after half a revolution oppo-
site the south pole, and the influence of the
south pole tends to produce an opposite
current to that of the north pole. Here we
an alternate current" dynamo ma
chine.
As the coil, or armsture, rotates with
great speed-some hundreds of revolutions
per minute-these currents, in alternating
directions. succeed each other very rapidly,
if an electric arc lamp is placed Oh the
s.
nat ~ ~. ~ W =. 'n.s t" 30 s.an
ae .Ta .i"' Il uu.ten' 10 een.
.ithnro ~ ~ torn,i naIa 80 tba Inma ~. ou'
1873 Is .harnnn .hn;r III ~ - \ ~
1I NV. naiIs.n .ntn u."a.uS.u.n la 10,
next instant becomes the south pole where
t;,oes - Inv aaoond .ha "a ayaas oUodnaa a"ly
~ ae Go ~ ~ so ~ - - .n.oS .ouuoeu ~
inrn sa a;ra a. :, 4 ouiieho was III one uhl-
rho Inmn ba. ,o +;,,o - ~. ooo,, - .o.
~ n ~ i ~ aas ~ ~ Ia W ~. oHoi, = ooes
20 ouo oelore sne oppositeIy ulrscteo
' h phsses 'naousn i. ano produces
,Ge e ~ "s Tue previous m6o one. NO
~ opselyapie' Tue impression
1ioouceu ny .ue elowlnH carbon on the nu-
nan eye ~ iesatheu oy 'he Ietiha 1or a 1ar
oneer perioo !nan Tue onratlon OF one
urge OF eleotrlclty thfongh the lamp, and
: nov zone DeIore 1no enect produced by
,ne suoceeuinR opposite wave make its I'M
sssnon ~ ~ nerves. ne 1aploohKoH
aMps useu lately on the 1hames enoank-
"le ilesnS ior tnis system OF electrlc
iGn'ahR WIN ai1erhatlng currents.
LII CONTINUOUS current dynamo, which
va SSAAS PNi pooCo, ouOA as