Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1917-02-03
CONSTRUCTION FUNCTIONS GENERATORS MOTORS
AUTOMOBH lists
(sy Special Permission from Motor
Age.

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electrical energy or electrical en-.
ergy into mechanical energy by means
OF electromagnetic induction. The DIV.
namo, when used to transform me-
chanical power into electrical energy.
Is called a generator. and when IL is
used TO transfer electrical energy into
!. mechanical energy Il Is called a
motor Bear in mind that the gener-
ator does not create electricity, but
simply imparts energy to IL, just as
energy is impaired TO the electricity
as II passes through the primary cell.
The dynamo consists, fundamental
~, OF two parts-a magnetic field,
which may be produced by permanent
magnets or electromagnets, and an
armature, which consists of loop of
wire or a number OF loops, usually
wound or mounted on an iron core or
frame and so arranged that there may
be a relative movement OF the mag
netic lines Of force forming the mag
netic field and the loop OF wire. The
movement OF the loop OF wire and the
magnetic lines OF force with respect
TO each other results in there being
an electrical pressure produced In the
loop.
Simple Alternator
IL single loop OF wire is revolved in
the magnetic field of a permanent
magnet, as shown in Figure 1, there
VIII be an electrical pressure induced
In the two sides Of the loop. II the
terminals of the loop be connected to
two metal rings G and y, upon which
brushes rest, this induced electrical
pressure win produce current in
circuit. such as q lamp, when It is
connected to the brushes. The direc-
ton OF the induced electrical pressure
IN the two sides Of the loop may be
determined by simple application of
Fleming's generator rule, as given in
previous instalment.
The motion OF one side of the loon
with respect to the magnetic field Ia
just the reverse to the motion Of the
other side. As result OF this differ.
ence In motion Of the two sides Of the
loop with respect TO the magnetic field
the electrical pressure induced in q
side OF the loop VIII be from the OBJ
server while that induced IN the other
side will be toward the observer.
These eiectficAl prezsnfes are M
series, and since their directions are
opposite with respect to the observer,
they both tend 70 produce current
IN the same direction around the
loop. There wiz be no induced cleo.
trical pressure In the ends Of the
loop, since they cut no lines OF force.
The electrical pressure Induced In
either side Of the loop at any instant
VIII depend upon the number of mag
netic lines cut IN one second, or the
rate at which the lines are being, cut.
This rate Of cutting Of the maentfc
lines will depend upon the length Of
the two sides OF the loop IN the mag.
netic field. the strength OF the mag.
netic field and the number of reyolu.
lions per second. Assuming the
strength OF the magnetic field is uni.
form, that II is the same at every
part OF the field and It remains con.
slant IN value and the loop reyolyes
about its axis at q constant speed,
then the induced pressure In the loop
VIII change In value. due only to a
change In the direction Of motion of
the two sides OF the loop with re.
spect TO the magnetic field. ]
Thus. when the loop rs In the hori.
zontai position. the direction. of the
field also being horizontal the two
hides of the loop viii be moving IN a
path, just for an instant, perpendicular
IN the direction OF the MAGNETIC field
and the rapidity with which the two
sides OF the loop are cutting the lines
OF force Is greatest, hence the Induced
electrical pressure IN the loop e zero
for this position OF the loop. The value
OF the induced electrical pressure for
positions intermediate between those
Just given will depend upon how fast
the sides of the loop are actually NOV.
ing across the magnetic field.
A curve may be drawn which viii
show graphically the relation between
: the induced electrical pressure In the
loop and It's position with respect to a
plane perpendicular to the magnetic
Held. Draw line A B, as in Figure :.
and divide this. line into. say. u
equal parts; each part win then cor.
respond to 80 degrees movement Of
the coil or loop about its axis Start
with the coil In q plane perpendicular
to the magnetic field and let his cor
respond to the point A In the figure;
the electrical pressure induced in the
loop for any movement from this posi-
ton should be measured off to q con-
venient scale on perpendicular line
drawn through the point on A B cor.
responding to the displacement Of the
loop. Thus, the electrical pressure win
be q maximum when the loop has TO
tated through an angle Of 80 degrees.
II then decreases as the angle in.
creases from 80 degrees to $50 degrees
and becomes equal TO zero when the
loop has rotated through an angle OF
$50 degrees
The direction Of the movement Of
the two sides Of the loop with respect
to the magnetic field changes jus: as
the coli passes the $50 degree posi-
ton and, as result. the direction OF
the induced electrical pressure
changes. The numerical value of the
reduced pressure for the second $50
degrees are identical to those for the