Audubon County Republican. [volume] (Audubon, Audubon Co., Iowa) 1885-1894, 1891-04-23
MYSTERIOUS DYNAMO.
1T is AN OBJECTIONABLE MYS-
Terry TO MANY.
Hut When Once Explained IL Becomes
Like an Open Book and II Is
M ghty Interesting Road
ing just Now.

aver constructed was that made by
Faraday. says acknowledge. This
great physicist the prince of expert
mentors, rs he has boon called, dis
covered that when disc or HAT plate
OF copper was made TO rotate between
tho poles Of powerful magnet
currents were produced in tho plato
from the center outward BY making
II wire touch the revolving plato with
one OF its ends and bringing the other
ono In contact with tho rim he found
that " current OF electricity passed
along the wiro and could be made TO
Indicate Its existence by DETECTING tho
needle OF n galvanometer. decompos-
ing u chemical solution, or by any OF
the well-known effects produced by
electricity in motion.
Faraday saw tho Importance of this
| discovery and the great uses In the
way of practical application TO which
II might be put but he did not him
self stay to develop IL.
Dynamo and magnetic electric ma
chimes consist essentially OF coil OF
wiro---''the armaturen ~ IL Is called
rotating between tho poles of II
largo magnet the poles being bent
round so as TO approach each Other
and have tho nrmnturo between thom.
This magnet may be either porma-
nent magnet of hard steel on an cleo
tro-magnet consisting of wiro coiled
round soft iron coro, II current Of
electricity being made TO circle round
tho wire coil, and thus mugnetizing
the iron coro while II lasts. II Ia tho
latter arrangement which Is almost
universally used now, though tho mag
neto machines with permanent mag
nets were the earliest form.
A magnet produces mn influence In
tho neighborhood around IT, and this
surrounding neighborhood IL known
rs tho "iiod OF force of tho magnet
|. o., the sphere in which its influence
can DO felt, A magnetic needle or bit
OF iron-llling placed In this field sets
itself TO point along tho dimes OF
force" of tho fold-that Is, tho lines
along which tho magnetic force acts,
| aad which form curves round tho
magnet running out, rs II were, from
pole TO pole, and curving round 10 the
| other. Any ono may see the form Of
these lines OF force for himself by
placing bar-magnet underneath u
| sheet OF paper and then sprinkling
iron-iilings on the paper.
On tapping this tho filings will set
themselves along the lines of force In
beautiful regular curves. Hero tho
| small fragments of iron are themselves
made magnets while under tho In
| iluonce OF the powerful magnet In
whose "iield" they are, and therefore
place Themselves longthways along tho
| lines OF forcc--that Is, along tho line
Of action Of the resultant magnetic
force Mt the place whore each one Is.
When coil OF wire or nrmature IL
made to revolyo rapidly in tho strong
| field OF force which occupies the spnco
between the poles OF II powerful electro
magnet currents IRE produced In the
coil. These currents alter their di-
roction through the coil every time the
latter changes It's position with refer
ence to tho poles Of the magnet. The
side Of the coil which was opposite tho
north polo is after half revolution
| opposite the south pole, and the in
| llucnco OF the south pole tonds TO pro-
ducc an opposite current 10 that Of the
north pole. Here wo have an .'alter-
nate current dynamo machine
As the call or armature rotatcs with
| great speed hundreds Of rcvo-
lutions per minutc--thosc currents, In
! alternating directions, succeed each
other very rapidly. and II an electric
| arc-lamp IL placed on the current IL
will be lit up. In this case il is not
necessary that tho current be sent
round the circuit in one direction only,
| but although the terminals OF the lamp
arc constantly changing their polarity
that Is. the north pole whore tho
| current enters the next instant becomes
| the south pole where the current leaves
--yot us this occurs many times in one
second, the effect produced is the same
AS II the current was In one uniform
| direction.
The lamp has no time TO get cool; II
does not go out before the oppositely
| directed current passed through IL and
| produces the same effect rs the previous
one. No pickering is observable. Tho
impression produced by the glowing
carbon on tho human eye is retained
by tho retina for far longer period
than the duration OF one surge OF cleo
tricity through tho lamp, and is not
gone before the effect produced by the
succeeding opposite wave makes its
| impression on our nerves. The
Jablochkoff lamps used lately on the
Thames embamtment are meant for
this system OF electric lighting with
alternating currents.