POWER, AND VARIOUS OTHER ELECTRICAL MANIFESTATIONS
It would be difficult to mention any direction in human activity where
electricity does not serve as an agent in some form or manner. Man has
learned that the Creator gave this great power into the hands of man to
use, and not to curse.
When the dynamo was first developed it did not appear possible that it
could generate electricity, and then use that electricity in order to
turn the dynamo in the opposite direction. It all seems so very natural
to us now, that such a thing should practically follow; but man had to
learn this.
Let us try to make the statement plain by a few simple illustrations. By
carefully going over the chapter on the making of the dynamo, it will be
evident that the basis of the generation of the current depends on the
changing of the direction of the flow of an electric current.
Look at the simple horse-shoe magnet. If two of them are gradually moved
toward each other, so that the north pole of one approaches the north
pole of the other, there is a sensible attempt for them to push away
from each other. If, however, one of them is turned, so that the north
pole of one is opposite the south pole of the other, they will draw
together.
In this we have the foundation physical action of the dynamo and the
motor. When power is applied to an armature, and it moves through a
magnetic field, the action is just the same as in the case of the hand
drawing the north and the south pole of the two approaching magnets from
each other.
The influence of the electrical disturbance produced by that act
permeated the entire winding of the field and armature, and extended out
on the whole line with which the dynamo was connected. In this way a
current was established and transmitted, and with proper wires was sent
in the form of circuits and distributed so as to do work.
But an electric current, without suitable mechanism, is of no value. It
must have mechanism to use it, as well as to make it. In the case of
light, we have explained how the arc and the incandescent lamps utilize
it for that purpose.
But now, attempting to get something from it in the way of power, means
another piece of mechanism. This is done by the motor, and this motor is
simply a converter, or a device for reversing the action of the
electricity.
Attention is called to Figs. 120 and 121. Let us assume that the field
magnets A, A are the positives, and the magnets B, B the negatives. The
revolving armature has also four magnet coils, two of them, C, C, being
positive, and the other two, D, D, negative, each of these magnet coils
being so connected up that they will reverse the polarities of the
magnets.
[Illustration: _Figs. 120-121._ ACTION OF MAGNETS IN A DYNAMO]
Now in the particular position of the revolving armature, in Fig. 120,
the magnets of the armature have just passed the respective poles of the
field magnets, and the belt E is compelled to turn the armature past the
pole pieces by force in the direction of the arrow F. After the armature
magnets have gone to the positions in Fig. 121, the positives A try to
draw back the negatives D of the armature, and at the same time the
negatives B repel the negatives D, because they are of the same
polarities.
This repulsion of the negatives A, B continues until the armature poles
C, D have slightly passed them, when the polarities of the magnets C, D
are changed; so that it will be seen, by reference to Fig. 122, that D
is now retreating from B, and C is going away from A--that is, being
forced away contrary to their natural attractive influences, and in Fig.
123, when the complete cycle is nearly finished, the positives are again
approaching each other and the negatives moving together.
[Illustration: _Figs. 122-123._ CYCLE ACTION IN DYNAMO]
In this manner, at every point, the sets of magnets are compelled to
move against their magnetic pull. This explains the dynamo.
Now take up the cycle of the motor, and note in Fig. 124 that the
negative magnets D of the armature are closely approaching the positive
and negative magnets, on one side; and the positive magnets C are
nearing the positive and negatives on the other side. The positives A,
therefore, attract the negatives D, and the negative B exert a pull on
the positives C at the same time. The result is that the armature is
caused to revolve, as shown by the dart G, in a direction opposite to
the dart in Fig. 120.
[Illustration: _Figs. 124-125._ ACTION OF MAGNETS IN MOTOR]
When the pole pieces of the magnets C, D are about to pass magnets A, B,
as shown in Fig. 125, it is necessary to change the polarities of the
armature magnets C, D; so that by reference to Fig. 126, it will be seen
that they are now indicated as C-, and D+, respectively, and have moved
to a point midway between the poles A, B (as in Fig. 125), where the
pull on one side, and the push on the other are again the same, and the
last Figure 127 shows the cycle nearly completed.
The shaft of the motor armature is now the element which turns the
mechanism which is to be operated. To convert electrical impulses into
power, as thus shown, results in great loss. The first step is to take
the steam boiler, which is the first stage in that source which is the
most common and universal, and by means of fuel, converting water into
steam. The second is to use the pressure of this steam to drive an
engine; the third is to drive the dynamo which generates the electrical
impulse; and the fourth is the conversion from the dynamo into a motor
shaft. Loss is met with at each step, and the great problem is to
eliminate this waste.
[Illustration: _Figs. 126-127._ POSITIONS OF MAGNETS IN MOTOR]
The great advantage of electrical power is not in utilizing it for
consumption at close ranges, but where it is desired to transmit it for
long distances. Such illustrations may be found in electric railways,
and where water power can be obtained as the primal source of energy,
the cost is not excessive. It is found, however, that even with the most
improved forms of mechanism, in electrical construction, the internal
combustion engines are far more economical.
_Transmission of Energy_
One of the great problems has been the transmission of the current to
great distances. By using a high voltage it may be sent hundreds of
miles, but to use a current of that character in the cars, or shops, or
homes, would be exceedingly dangerous.
To meet this requirement transformers have been devised, which will take
a current of very high voltage, and deliver a current of low tension,
and capable of being used anywhere with the ordinary motors.
THE TRANSFORMER.--This is an electrical device made up of a core or
cores of thin sheet metal, around which is wound sets of insulated
wires, one set being designed to receive the high voltage, and the other
set to put out the low voltage, as described in a former chapter.
These may be made where the original output is a very high voltage, so
that they will be stepped down, first from one voltage to a lower, and
then from that to the next lower stage. This is called the "Step down"
transformer, and is now used over the entire world, where large voltages
are generated.
ELECTRIC FURNACES.--The most important development of electricity in the
direction of heat is its use in furnaces. As before stated, an intense
heat is capable of being generated by the electric current, so that it
becomes the great agent to use for the treatment of refractory material.
In furnaces of this kind the electric arc is the mechanical form used to
produce the great heat, the only difference being in the size of the
apparatus. The electric furnace is simply an immense form of arc light,
capable of taking a high voltage, and such an arc is enclosed within a
suitable oven of refractory material, which still further conserves the
heat.
WELDING BY ELECTRICITY.--The next step is to use the high heat thus
capable of being produced, to fuse metals so that they may be welded
together. It is a difficult matter to unite two large pieces of metal by
the forging method, because the highest heat is required, owing to their
bulk, and in addition immense hammers, weighing tons, must be employed.
Electric welding offers a simple and easy method of accomplishing the
result, and in the doing of which it avoids the oxidizing action of the
forging heat. Instead of heating the pieces to be welded in a forge, as
is now done, the ends to be united are simply brought into contact, and
the current is sent through the ends until they are in a soft condition,
after which the parts are pressed together and united by the simple
merging of the plastic condition in which they are reduced by the high
electric heat.
This form of welding makes the most perfect joint, and requires no
hammering, as the mass of the metal flows from one part or end to the
other; the unity is a perfect one, and the advantage is that the metals
can be kept in a semi-fluid state for a considerable time, thus assuring
a perfect admixture of the two parts.
With the ordinary form of welding it is necessary to drive the heated
parts together without any delay, and at the least cooling must be
reheated, or the joint will not be perfect.
The smallest kinds of electric heating apparatus are now being made, so
that small articles, sheet metal, small rods, and like parts can be
united with the greatest facility.