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MANAGERS AND PROJECTIONISTS 51
to, and may be compared with water, but it must be remembered that the similarity exists in similarity of action only.
Water may be subject to physical examination. We can feel it, watch its action and weigh it. On the other hand, electricity is an absolutely impalpable substance — if we may even call it a substance. It apparently is without weight. We cannot see it, except in the form of light, which is not the current itself but a product of its action. We cannot feel it, except in the form of a "shock" occasioned by the current passing through the tissues of the body.
Voltage corresponds in effect, or in its action, to the pressure of water in a pipe, or to the pressure of steam in a boiler. A dry battery, such as is used for electric bells, has a pressure of approximately one volt. It imparts that pressure to wires connected to its terminals, so that if you attach two wires to such a battery, they will, at any portion of their length, have an electrical pressure of one volt. If you connect the zinc of a second battery with the carbon of the first battery by means of a short piece of wire, and then attach two other wires to the two remaining binding posts, you will have what is known as "series" connection, and a resultant pressure of two volts between the two last named wires. A third battery connected in series would raise the pressure to three volts, and so on indefinitely.
Instead of using batteries for producing light and power, which would be entirely impractical, we use a machine called a dynamo, each one of which is designed and built to produce a certain voltage, which may be anywhere from one to 500 volts D. C., or from one to 6,000 volts A. C.
Remember that voltage corresponds to pressure, and is similar 'in its action to pressure in a steam boiler, but that voltage acts only between the positive and negative wires of the dynamo or battery which generated it, and that the positive attached to one generator has no affinity or attraction to or for the negative attached to another dynamo, or for the ground, except as it offers a path to the negative of the generator to which the positive is attached. Get this fact firmly fixed in your mind. Ninety-nine out of every hundred nonelectricians believe current generated by a dynamo seeks to escape into the ground. This is not so, except insofar as the ground may offer a path of electrical conductivity between two wires of opposite polarity. See page 6.
AMPERE is the term used to denote quantity. It represents the volume of current flowing through, or along a wire,