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.
|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.
|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.
|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.
|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.