Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1916-12-23

81.
through the solenoid viii be greatly
increased.
The number of lines Of force pei
square centimeter in the magnetic ma
terial is called the induction density
and it is usually represented by the
letter B. The permeability of a ma
terial may be thought Of as the abiE
ity of the material to conduct mag
netic flux as compared to air. In
making up good magnetic circuit il
is always desirable to have materials
Of high personalities, in order that
the reluctance of the magnetic circuit
may be low.
The magnetomotive force acting as
q magnetic circuit, the reluctance OF
the circuit and the magnetic: flux pro-
dnced are related to Ane another just
as the electrical pressure in an cleo
trical circuit, its resistance and the
current produced arel related to one
another. This relation may be ex-
pressed as follows:
magnetomotlye force
Magnetic flux - -
reluctance
Reluctance in Series and Parallel
A magnetic circuit may be composed
of several reluctances connected in
series of parallel or accumulation of
the two methods just as an electrical
circuit may be composed of several re-
sistances connected in series or par
allel or a combination of the two meth
DDS.
If an air gap be in an iron ring,
as shown In figure 3, the magnetic
circuit composed Of the iron ring and
air gap will CONSTITUTES, a magnetic cir
cult in which two reluctances are in
series. The total reluctance of such
a circuit is equal to the sum of the
reluctance of the different parts, just
as the total resistance of series cleo
trical circuit is equal to the sum of the
resistance of the different parts.
II two iron rings be placed side by
side and a winding placed about both
of them, the two rings will constitute
magnetic circuit in which two re.
luctances are in parallel The two
rings and winding may be arranged as
shown in figure 8, but the reluctances
of the two rings are still in parallel.
Magnetomotive forces in series and
parallel magnetomotive forces may be
connected in series ond parallel just
as electromotive forces may be con-
nected in series and parallel. For ex-
ample. the magnetomotive force of
winding A in figure is acting on the
same magnetic circuit as the magnetic
motive force of winding B. If these
two magnetomotive forces both tend to
prolong a magnetic flux around the
iron ring in the same direction, the
total magnetomotive force acting on
the magnetic circuit will be equal to
the sum of the two. If, however, the
two magnetomotive forces tend to pro-
duce magnetic flux abound the iron
ring in opposite directidps. the total or
effective magnetomotiye force acting
on the magnetic circuit will be equal
to the difference between the two
magnetomotive forces The direction
of the effective magnetomotive forces
will correspond to the direction of the
larger of the two magnetomotiye
forces
ure 5 is composed of number Of re-
luctances in series and two magnetic
motive forces in series. Two magnetic
motive forces are shown acting in
series on two magnetic circuits, con-
nected in parallel in figure g. The
magnetic circuits of four pole gen.
orator or motor are shown in figure z.
In figures 2 to Z, inclusive. the dotted
lines indicate the paths of the lines of
force. The magnetomotive force act
ing on each of the magnetic circuits
in figure is equal to the sum Of the
magnetomotive forces Of the two coils
wound around the circuit. Each coil
is connected to two magnetic circuits
in ..gure {, and only one-half as many
ampere-turns are required in each coil
with this arrangement as would be re-
quired II the coils were wound around
the outside portion of the magnetic