Volt

“ We will now connect with our laboratory current a 32-candle-power lamp, an ammeter, and a wattmeter, all in series, Fig. 18, and in parallel with these a volt meter. This last instrument indicates the electric pressure. Its mechanism will be examined later. The volt meter indicates 110 volts and the ammeter shows that one ampere is passing. [41] The filament in the lamp resists the passage of the current. It gets quite hot and gives forth as much light as thirty-two candles. Its resistance is just such that 110 volts of pressure send one ampere through it. ”

“ The volt-coulomb is very seldom used, and the unit of Electric Activity
or Power (see Power, Electric) , the volt-ampere, is universally used.
This unit is sometimes called the Watt, q. v., and it indicates the rate
of expenditure or of production of electric energy.
The storing up in a static accumulator or condenser of a given charge of
electricity, available for use with a given change of potential
represents potential electric energy.
The passing of a given quantity through a conductor with a given fall of
potential represents kinetic electric energy. ”

“ As a unit of electromotive force, the International Volt, which is the electromotive force that, steadily applied to a conductor whose resistance is one international ohm, will produce a current of one international ampere. ”

“ In external appearance they are not distinguishable from ammeters.
FIG. 236.—A voltmeter.
The unit of electromotive force is called the volt. The voltage of a dry cell is approximately 1.5 volts, and the voltage of a voltaic cell and of a gravity cell is approximately 1 volt.
316. Current, Voltage, Resistance. We learned in Section 287 that the strength of a current increases when the electromotive force increases, and diminishes when the electromotive [345] force diminishes. Later, in Section 288, we learned that the strength of the current decreases as the resistance in circuit increases. ”

“ 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 [7] water from escaping. Thus, you see, the volt does not itself represent electricity, but only the pressure which forces it through the wire. ”

“ It is the electrical resistance of a rod of copper of a certain length and thickness when at a certain temperature. The electric pressure or difference of potential which will send a certain amount of current, called an 'ampere,' through a conductor the resistance of which is an ohm, is one volt. ”

“ Currents from the ten-thousandth of an ampere to ten thousand amperes, electrical pressures from a minute fraction of a volt to 100,000 volts, come within the range of his instruments, while the private consumer of electric energy is provided with a meter recording Board of Trade units. ”

“ The opposition which one’s self-induced conscience offers depends upon how rapidly one starts. It’s volts which make electrons move and so the conscience which opposes them will be measured in volts. Therefore we say that a coil has one henry of inductance when an electron stream 85which is increasing one ampere’s worth each second stirs up in the coil a conscientious objection of one volt. ”

“ When, however, everything is in the best proportion, i.e. length of arc, size of carbons, and current passing, the potential at the arc lamp terminals required is approximately 45 volts, and this may be taken as a fixed figure for any current. ”

“ The weight of copper deposited and the time taken are used to calculate the current strength.
Fig. 71.
76. Unit of Quantity; The Coulomb is the quantity of electricity given, in one second, by a current having a [55] strength of one ampere. Time is an important element in considering the work a current can do.
Fig. 72.
77. Electrical Horse-power; The Watt is the unit of electrical power. A current having the strength of one ampere, and an E. M. F. of one volt has a unit of power. 746 watts make one electrical horse-power. Watts = amperes × volts. Fig. ”

“ For any given size of wire and distance apart of wires there is a certain voltage at which the critical density or critical gradient is reached, where the air breaks down and luminosity begins—the critical voltage where corona manifests itself. ”

“ Voltage.—This plays an important part in ignition. Voltage is that quality which gives pressure or intensity to a current. It is the driving force, just as a head of water gives pressure to a stream of water.
High and Low Voltage.—A high tension current,—that [105] is, one having a high voltage, will leap across a gap, whereas a low voltage must have an easy path. When the ends of a wire in a circuit are separated, air acts as a perfect insulator between them, and the slightest separation will prevent a low current from jumping across. ”

“ Amalgamation of the zinc
prevents local action. Chemically pure zinc is also exempt from local
action, and can be used in an acid battery without amalgamation. (See
Amalgamation.)
(b) The same term has been employed to indicate the eddy or foucault
currents in dynamo electric machines. (Sec Current, Foucault.)
Activity.
The rate of doing work; the work done per second by any expenditure of
energy. The activity of a horse-power is 550 foot lbs. per second, or
746 volt-coulombs per second. The practical electric unit is the
volt-ampere, often called the watt. (Sec Energy, Electric.) ”

“ But the electro-motive force ascribed by Volta to the metals when in contact is a force which, as long as a free course is allowed to the electricity it sets in motion, is never expended, and continues to be exerted with undiminished power, in the production of a never-ceasing effect. ”

“ Current Electricity.—Whenever electricity flows in a wire, or other conductor, it acts like water flowing through a pipe and it is then called current electricity. The two most common ways to generate a current of electricity is by means of a chemical battery and by a dynamo electric machine.
A current of electricity may have a small current strength, as its quantity is called, and a high voltage, as its pressure is called, like the discharge of a Leyden jar, or it may have a large current strength and a low voltage, as a current generated by a battery. ”

“ In ordinary acceptance among engineers and practical working electricians, electro-motive force is considered as pressure and it is measured in units called volts. The usual standard for testing and comparison is a special form voltaic cell, called the Clark cell. ”

“ The time-constant of the discharging resistance is such that the voltage is point eight three, of its peak three thousand volts, giving a good check of the alloy."
"I should think so," groused Channing. "Eighty-three percent of three thousand volts is just shy of twenty-five hundred volts. ”

“ We have means of searching into the constitution of water beyond any that are afforded us by the action of heat, and among these one of the most important is that force which we call voltaic electricity, which we used at our last meeting for the purpose of obtaining light, and which we carried about the room by means of these wires. ”

“ FARADAY’S discovery that, in combinations like those in which a voltaic current was known to produce motion, motion would produce a voltaic current, naturally excited great attention among the scientific men of Europe. ”

“ Common electricity is excited upon non-conductors, and is readily carried off by conductors and imperfect conductors. Voltaic electricity is excited upon combinations of perfect and imperfect conductors, and is only transmitted by perfect conductors or imperfect conductors of the best kind. ”

“ He says, ‘There is a very singular analogy that exists between the rays at the violet end of the spectrum, hydrogen gas, and the negative pole of the voltaic battery; and opposed to it stands the analogy of the rays at the red end of the spectrum to positive electricity; they produce opposite effects to the first-mentioned arrangement, but act similar to each other. ”

“ Among the startling facts brought out in these experiments is that although a current of electricity, either direct or alternating, from ordinary dynamos under fifteen hundred or two thousand volts electro-motive 'force will kill, yet under alternations of a million to a million and a half per second a voltage of fifty thousand produces no shock or injury. ”

“ In one the exciting armature is rotated, producing the working voltage of 250, 500 or 1000 volts. In the other gap are pivoted two coils wound on an iron core and connected at nearly a right angle to each other. ”

“ THE RÖNTGEN RAYS In the chapter on electricity in the atmosphere we saw that whereas air at ordinary pressure is a bad conductor, its conducting power increases rapidly as the pressure is lowered. Roughly speaking, if we wish to obtain a spark across a gap of 1 inch in ordinary air, we must have an electric pressure of about 50,000 volts. ”

“ In one the body of a person was subjected to the rapidly-alternating pressure of an electrical oscillator of two and a half million volts; in the other a small incandescent lamp was lighted by means of a resonant circuit grounded on one end, all the energy being drawn through the earth electrified from a distant transmitter. ”

“ Chemical decomposition.—The chemical powers of the voltaic current, and their subjection to certain laws, are also perfectly well known.
279. iv. Physiological effects.—The power of the voltaic current, when strong, to shock and convulse the whole animal system, and when weak to affect the tongue and the eyes, is very characteristic.
280. v. Spark.—The brilliant star of light produced by the discharge of a voltaic battery is known to all as the most beautiful light that man can produce by art. ”

“ Since 1799 there have been discovered additional sources, among which are voltaic electricity, or electricity produced by chemical action, such as is manifested when two dissimilar metals are brought near each other or together, and electrical manifestations produced by a decomposing action, one upon the other through a suitable medium; inductive electricity, or electricity developed or induced in one body by its proximity to another body through which a current is flowing ”

“ If one light is of less intensity than another and both of them receive their impulses from the same source, there must be something which interferes with that light which shows the least brilliancy. Electricity can also be interfered with, and this interference is called resistance.
Voltage.—Water may be made to flow with greater or less force, or velocity, through a pipe, the degree of same depending upon the height ofp. 61 the water which supplies the pipe. So with electricity. It may pass over a wire with greater or less force under one condition than another. This force is called voltage. ”

“ You know that if you have a very great pressure you can force a quantity through a small conductor. This is the principle upon which the arc-lamps are run. Every arc-lamp takes about 40 to 50 volts and from 5 to 10 ampères to produce the light, and they are connected with the wires as shown in Fig. ”

“ While I have not, as yet, actually effected a transmission of a considerable amount of energy, such as would be of industrial importance, to a great distance by this new method, I have operated several model plants under exactly the same conditions which will exist in a large plant of this kind, and the practicability of the system is thoroughly demonstrated. The experiments have shown conclusively that, with two terminals maintained at an elevation of not more than thirty thousand to thirty-five thousand feet above sea-level, and with an electrical pressure of fifteen to twenty million volts, the energy of thousands of horse-power can be transmitted over distances which may be hundreds and, if necessary, thousands of miles. ”

“ In every point of the space surrounding such a conductor, there acts a force pushing positive electricity one way and negative electricity the opposite way. If the charged body is positively electrified, the potential will be positive all around it, but higher close to the body and lower the farther we recede from it. We must conceive a charge as a something which is adhering to a conducting surface; where there is no conductor there can be no charge, though there may be potential. ”

“ Electric Potential.—Suppose then that we have a conductor charged with electricity; we may imagine its surface to be divided up into small unequal areas, each of which carries a unit charge of electricity. If we consider lines of electric force to be drawn from the boundaries of these areas, they will cut up the space round the conductor into tubular surfaces called tubes of electric force, and each tube will spring from an area of the conductor carrying a unit electric charge. ”

“ When a spark of static electricity jumps a long distance, we say that the charge has a high potential; that is, it has a high electrical pressure. Potential, for electricity, means the same as pressure, for water. The greater the potential, or electromotive force (E.M.F.) of a cell, the greater its power to push a current through wires. (See "Study," § 296 to 305, with experiments.) ”