A-B-C of Electricity

by Wm. H. Meadowcroft

This word "volt" does not mean any weight, as the word "pound" weight does. You all know that if you have a pound of water you must have something to hold it, because it has weight, and, consequently, occupies some space. But electricity itself has no weight and therefore cannot occupy any space.

When we desire to carry water into a house or other building we do so by means of hollow pipes, which are usually made of iron. This is the way that water is brought into houses in cities and towns, so that it may be drawn and used in any part of a dwelling. Now, the principal supply usually comes from a reservoir which is placed up on high ground so as to give the necessary pounds of pressure to force the water up to the upper part of the houses. If some arrangement of this kind were not made we could get no water in our bedrooms, because, as you know, water will not rise above its own level unless by force.

The water cannot escape as long as there are no holes or leaks in the iron pipes, but if there should be the slightest crevice in them the water will run out.

In electricity we find similar effects.

The electricity is carried into houses by means of wires which are covered, or insulated, with various substances, such, for instance, as rubber. Just as the iron of the pipes prevents the water from escaping, the insulation of the wire prevents the escape of the electricity.

Now, if we were to cause the pounds of pressure of water, in pipes of ordinary thickness, to be very greatly increased, the pipes could not stand the strain and would burst and the water escape. So it is with electricity. If there were too many volts of pressure the insulation would not be sufficient to hold it and the electricity would escape through the covering, or insulation, of the wire.

It is a simple and easy matter to stop the flow of water from an ordinary faucet by placing your finger over the opening. As the water cannot then flow, your finger is what we will call a non-conductor and the water will be retained in the pipe.

We have just the same effects in electricity. If we place some substance which is practically a non-conductor, or insulator, such as rubber, around an electric wire, or in the path of an electric current, the electricity, acted upon by the volts of pressure, cannot escape, because the insulation keeps it from doing so, just as the iron of the pipe keeps the water from escaping. Thus, you see, the volt does not itself represent electricity, but only the pressure which forces it through the wire.

There are other words and expressions in electricity which are sometimes used in connection with the word "volt." These words are "pressure" and "intensity." We might say, for instance, that a certain dynamo machine had an electromotive force of 110 volts; or that the intensity of a cell of a battery was 2 volts, etc.

We might mention, as another analogy, the pressure of steam in a boiler, which is measured or calculated in pounds, just as the pressure of water is measured. So, we might say that 100 pounds steam pressure used through the medium of a steam-engine to drive a dynamo could thus be changed to electricity at 100 volts pressure.