New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1895-07-08
sELF-INDUCTION IN AN ELECTRIC WIRE.
THE ANNOYANCE 1T CAUSES. AND HOW IT MAY
ONERCOME

THE ANNOYANCE IT CAUSES. AND HOW IT MAY
BE OVERCOME.
phenomenon which embarrasses the practical
electrician In many ways. but especially in teeg-
raphy and telephony is called self-inducton. Each
time the flow OF a current Is stopped or started. a
certain lag Is produced II by inertia This Is
ceedngiy short in point OF time: and It's extent de-
ponds somewhat on the size and length OF the con-
ductor and some other circumstances. So long as tho
current continues to flow In direction. there Is
no difficulty OF this kind: but II Is as II a certain
momentum had TO be acquired or overcome each
time the circuit Is closed and opered Hence In
sending messages ocean cable the speed
with which the letters are formed by nterrupting
and restoring the current, matter by what code OF
signals is limited by this tendency to blur in conse
quence Of selfnducton. The same trouble is en-
countered In long-distance telephony and Is
absolute barrier to this form OF communication
under the Atlantic Ocean. Now that alternating
currents for light and power coming into such
extensive use. the phenomenon manfests Itself In
another way certain amount OF voltage Is wasted
In overcoming the induction OF the line In the first
two Uses OF electricity here mentioned the effect
which Is chiefly lamented Is impairment OF eff
cheney; In the latter two 1t is the economical phase
OF the subject which attracts the most attention.
Both considerations have melted efforts to obviate
at least to lessen, this evil.
Self-nduction itself seems to result from the re-
sistance offered. by the dry air or Insulating coat
surrounding wire. 10 tne progress Oh tne
rings Of force which encircle conductor and
move forward when electric current flows That
resistance once overcome all goes we'll until the
current ceases when a corresponding change oc-
ours in the surrounding non-conductor or 'dialec-
trio" Now II a frequently interrupted and restored
current be led back through second wire parallel
with the first but insulated therefrom. fresh set
OF effects occurring simultaneously and showing
about the same Intensity. but always In the re-
verse direction from those produced by the other
wire. will be developed In the dalectric; and II the
two conductors placed pretty close together the
one set OF impulses will be partially offset by the
other. Experience having shown that self-induc-
ton could be lessened In this manner. some one
conceived the Idea OF making the supply and re-
turn wires concentric: that Is. one formed as
shell outside the other but separated from 1t by
layer OF Insulating material This is more costly
arrangement than laying two wires parallel to one
another doubt. but II IL expected to prove more
efficient. Tests recently made by Professor Guye
with the concentric conductors employed In connec
ton WITH electric lighting plant in Geneva
Switzerland. tend to confirm this belief Using the
core for lead" and the she'll for return. he
found that the voltage Of high-tension alternat-
Ing current would not show any greater drop In a
given distance than a continuous current would.