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Electricity

Temperature and Electricity

Professor Tyndall has shown that all variations of temperature, in metals at least, excite electricity. When the wires of a galvanometer are brought in contact with the two ends of a heated poker, the prompt deflection of the galvanometer-needle indicates that a current of electricity has been sent through the instrument. Even the two ends of a spoon, one of which has been dipped in hot water, serve to develop an electric current; and in cutting a hot beefsteak with a steel knife and a silver fork there is an excitement of electricity. The mere heat of the finger is sufficient to cause the deflection of the galvanometer; and when ice is applied to the part that has been previously warmed, the galvanometer-needle is deflected in the contrary direction. A small instrument invented by Melloni is so extremely sensitive of the action of heat, that electricity is excited when the hand is held six inches from it.

n. The power that causes all natural phenomena not known to be caused by something else. It is the same thing as lightning, and its famous attempt to strike Dr. Franklin is one of the most picturesque incidents in that great and good man's career. The memory of Dr. Franklin is justly held in great reverence, particularly in France, where a waxen effigy of him was recently on exhibition, bearing the following touching account of his life and services to science:

      "Monsieur Franqulin, inventor of electricity.  This
  illustrious savant, after having made several voyages around the
  world, died on the Sandwich Islands and was devoured by savages,
  of whom not a single fragment was ever recovered."

  Electricity seems destined to play a most important part in the
arts and industries.  The question of its economical application to
some purposes is still unsettled, but experiment has already proved
that it will propel a street car better than a gas jet and give more
light than a horse.

Velocity of Electric Light

On comparing the velocities of solar, stellar, and terrestrial light, which are all equally refracted in the prism, with the velocity of the light of frictional electricity, we are disposed, in accordance with Wheatstone's ingeniously-conducted experiments, to regard the lowest ratio in which the latter excels the former as 3:2. According to the lowest results of Wheatstone's apparatus, electric light traverses 288,000 miles in a second. If we reckon 189,938 miles for stellar light, according to Struve, we obtain the difference of 95,776 miles as the greater velocity of electricity in one second.

From the experiment described in Wheatstone's paper (Philosophical Transactions  for 1834), it would appear that the human eye is capable of perceiving phenomena of light whose duration is limited to the millionth part of a second.

In Professor Airy's experiments with the electric telegraph to determine the difference of longitude between Greenwich and Brussels, the time spent by the electric current in passing from one observatory to the other (270 miles) was found to be 0·109″ or rather more than the ninth part of a second ; and this determination rests on 2616 observations: a speed which would “girdle the globe” in ten seconds.

It is impossible in the existing state of human knowledge to give a satisfactory definition of electricity. The views of various authorities are given here to afford a basis for arriving at the general consensus of electricians.

We have as yet no conception of electricity apart from the electrified body; we have no experience of its independent existence. (J. E. H. Gordon.)

What is Electricity? We do not know, and for practical purposes it is not necessary that we should know. (Sydney F. Walker.)

Electricity … is one of those hidden and mysterious powers of nature which has thus become known to us through the medium of effects. (Weale's Dictionary of Terms.)

This word Electricity is used to express more particularly the cause, which even today remains unknown, of the phenomena that we are about to explain. (Amédée Guillemin.)

Electricity is a powerful physical agent which manifests itself mainly by attractions and repulsions, but also by luminous and heating effects, by violent commotions, by chemical decompositions, and many other phenomena. Unlike gravity, it is not inherent in bodies, but it is evoked in them by a variety of causes … (Ganot's Physics.)

Electricity and magnetism are not forms of energy; neither are they forms of matter. They may, perhaps, be provisionally defined as properties or conditions of matter; but whether this matter be the ordinary matter, or whether it be, on the other hand, that all-pervading ether by which ordinary matter is surrounded, is a question which has been under discussion, and which now may be fairly held to be settled in favor of the latter view. (Daniell's Physics.)

The name used in connection with an extensive and important class of phenomena, and usually denoting the unknown cause of the phenomena or the science that treats of them. (Imperial Dictionary.)

Electricity. . . is the imponderable physical agent, cause, force or the molecular movement, by which, under certain conditions, certain phenomena, chiefly those of attraction and repulsion, . . . are produced. (John Angell.)

It has been suggested that if anything can rightly be called "electricity," this must be the ether itself; and that all electrical and magnetic phenomena are simply due to changes, strains and motions in the ether. Perhaps negative electrification. . .means an excess of ether, and positive electrification a defect of ether, as compared with the normal density. (W. Larden.)

Electricity is the name given to the supposed agent producing the described condition (i. e. electrification) of bodies. (Fleeming Jenkin.)

There are certain bodies which, when warm and dry, acquire by friction, the property of attracting feathers, filaments of silk or indeed any light body towards them. This property is called Electricity, and bodies which possess it are said to be electrified. (Linnaeus Cumming.)

What electricity is it is impossible to say, but for the present it is convenient to look upon it as a kind of invisible something which pervades all bodies. (W. Perren Maycock.)

What is electricity? No one knows. It seems to be one manifestation of the energy which fills the universe and which appears in a variety of other forms, such as heat, light, magnetism, chemical affinity, mechanical motion, etc. (Park Benjamin.)

The theory of electricity adopted throughout these lessons is, that electricity, whatever its true nature, is one, not two; that this Electricity, whatever it may prove to be, is not matter, and is not energy; that it resembles both matter and energy in one respect, however, in that it can neither be created nor destroyed. (Sylvanus P. Thomson.)

In Physics a name denoting the cause of an important class of phenomena of attraction and repulsion, chemical decomposition, etc., or, collectively, these phenomena themselves. (Century Dictionary.)

A power in nature, often styled the electric fluid, exhibiting itself, when in disturbed equilibrium or in activity, by a circuit movement, the fact of direction in which involves polarity, or opposition of properties in opposite directions; also, by attraction for many substances, by a law involving attraction between substances of unlike polarity, and repulsion between those of like; by exhibiting accumulated polar tension when the circuit is broken; and by producing heat, light, concussion, and often chemical changes when the circuit passes between the poles, or through any imperfectly conducting substance or space. It is evolved in any disturbance of molecular equilibrium, whether from a chemical, physical, or mechanical cause. (Webster's Dictionary.)

In point of fact electricity is not a fluid at all, and only in a few of its attributes is it at all comparable to a fluid. Let us rather consider electricity to be a condition into which material substances are thrown. . .(Slingo & Brooker.)

[Transcriber's note: 2008 Dictionary: Phenomena arising from the behavior of electrons and protons caused by the attraction of particles with opposite charges and the repulsion of particles with the same charge.]

Electricity

How may electricity be called into activity?

By mechanical power, by chemical action, by heat, and by magnetic influence.

What is the most ordinary way of exciting electricity?

By friction.

Do we know any reason why the means above enumerated should develop electricity from its latent condition?

We are entirely ignorant  upon this subject.

When you rub a piece of paper with India-rubber, why does it adhere to the table?

Because the friction  of the India-rubber against the surface of the paper develops electricity, to which this adhesiveness is mainly to be attributed.

Does electricity present any appearance by which it can be known?

No; electricity, like heat, is in itself invisible, though often accompanied by both light  and heat.

When a substance, by friction or by any other means, acquires the property of attracting other bodies, in what state is it said to be?

It is said to be electrified, or electrically excited ; and its motion towards other bodies, or of other bodies towards it, is ascribed to a force called electric attraction.

Does an electrified body exercise any other influence than an attractive one?

It does ; for it will be found that light substances, after touching  the electrified body, will recede from it  just as actively as they approached it before contact. This is termed electric repulsion.

Thus, if we take a dry glass rod, rub it well with silk, and present it to a light pith ball, or feather, suspended from a support by a silk thread, the ball or feather will be attracted towards the glass. After it has adhered to it a moment, it will fly off, or be repelled. The same will happen if sealing-wax be rubbed with dry flannel, and a like experiment made; but with this remarkable difference, that when the glass repels the ball, the sealing-wax attracts it, and when the wax repels, the glass will attract. These phenomena are examples of electrical attraction  and repulsion.

What is a non-electrified body?

One that holds its own natural quantity of electricity undisturbed.

What happens when an electrified body touches one that is non-electrified?

The electricity contained in the former is transferred  in part to the latter.

Thus, on touching the end of a suspended silk-thread with a piece of excited wax, the silk will be excited, as will be shown by its moving towards a book, piece of metal, or any other object placed near it.

Do all bodies conduct or allow electricity to pass through them equally well?

Although there is no substance that can entirely prevent  the passage of electricity, nor any that does not oppose some resistance  to its passage, yet it moves with a much greater facility through a certain class of substances than through others. Those substances which facilitate its passage are called conductors; those that retard or almost prevent it, are called non-conductors.

What substances are good conductors of electricity?

The metalscharcoal, the earthwater, and most fluids, except oils, the human body, etc., are good conductors.

What substances obstruct the passage of electricity, or are “non-conductors”?

Glassresinoilsilksulphurdry air, etc., etc., are non-conductors.

What is an electrical machine?

An electrical machine is an arrangement by which quantities of electricity can be collected and discharged.

One type of the electrical machine most usually employed consists of a large circular plate of glass, mounted upon a metallic axis, and supported upon pillars fixed to a secure base, so that the plate can, by means of a handle, be turned with ease. Upon the supports of the glass, and fixed so as to press easily but uniformly on the plate, are four rubbers; and flaps of silk, oiled on one side, are attached to these, and secured to fixed supports by several silk cords. When the machine is put in motion, these flaps of silk are drawn tightly against the glass, and thus the friction is increased, and electricity excited.

Do we know what electricity is?

No; a complete and final answer to this question is no more possible than the answer to the question—what is life ? The theory  of electricity, however, opens up possibilities of the most fascinating nature; it gives us a wonderfully clear conception of which might be called the inner mechanism of electricity; and it even introduces us to the very atoms of electricity.

Give a short outline of the theory of electricity.

Early Theories.—Early writers on the nature of electricity supposed it to be either a fluid of peculiar properties or else two fluids whose properties were complementary to each other or of opposite kinds; Franklin held the one fluid theory. Later physicists arrived at the conclusion that whatever electricity might be, it was not a material substance. As an alternative it was suggested that electricity was a form of energy, but this proved untenable.

HOW ELECTRICITY IS PRODUCED BY THE ACTIVITY OF ELECTRONS

Diagram of the Atoms composing the finest point of a piece of Amber

ELECTRONS flying off from the SILK Atoms, across on to the AMBER Atoms, and so charging the Amber with what is called NEGATIVE Electricity

Diagram of the Atoms composing the thinnest possible thread of SILK; each Atom charged with innumerable NEGATIVE ELECTRONS whirling around within or on the Atoms.

Electron Theory.—This, with certain reservations, is held by the scientific world of today. All matter is believed to be constituted of minute particles called “atoms,” whose diameter has been estimated at about one millionth of a millimeter. Up to a few years ago the atom was believed to be quite indivisible, but it has been proved beyond doubt that this is not the case. An atom may be said to consist of two parts, one much larger than the other. The smaller part is negatively electrified, and is the same in all atoms; while the larger part is positively electrified, and varies according to the nature of the atom. The small negatively electrified portion of the atom consists of particles called “electrons,” and these electrons are believed to be indivisible units or atoms of negative electricity.

The electrons in an atom are not fixed, but move with great velocity, in definite orbits. They repel one another, and are constantly endeavoring to fly away from the atom, but they are held in by the attraction of the positive core. So long as nothing occurs to upset the constitution of the atom, a state of equilibrium is maintained and the atom is electrically neutral; but immediately the atom is broken up by the action of an external force of some kind, one or more electrons break their bonds and fly away to join some other atom. An atom which has lost some of its electrons is no longer neutral, but is electro-positive; and similarly, an atom which has gained additional electrons is electro-negative.

The Electric Current.—A current of electricity is believed to be nothing more or less than a stream of electrons, set in motion by the application of an electro-motive force. Some substances are good conductors of electricity, while others are bad conductors or non-conductors. In order to produce an electric current, that is a current of electrons, it is evidently necessary that the electrons should be free to move. In good conductors, which are mostly metals, it is believed that the electrons are able to move from atom to atom without much hindrance, while in a non-conductor their movements are hampered to such an extent that interatomic exchange of electrons is almost impossible.

Does electricity seem to exist in two different states or conditions?

It does; and to designate these two conditions, the terms positive and negative have been employed. Thus a body which has an overplus of electricity is called positive, and one that has less than its natural quantity is called negative.

Do light, heat, and electricity appear to have some properties in common?

They do ; each may be made, under certain circumstances, to produce  or excite  the other. All are so light, subtle, and diffusive, that it has been found impossible to recognize in them the ordinary characteristics of matter. Some suppose that light, heat, and electricity are all modifications  of some common principle.

Why does the fur of a cat sparkle and crackle when rubbed with the hand in cold weather?

Because the friction between the hand and fur produces an excitation of positive electricity  in the hand  and negative  in the fur, and an interchange of the two causes a spark, with a slight noise.

Why does this experiment work best in very cold weather?

Because the air is then very dry, and does not convey away  the electricity as fast as it is excited; if the air, on the contrary, were moist, the electricity would be conducted off  nearly as fast as it was excited by friction, and its effects would not therefore be so manifest.

With what velocity is electricity transmitted through good conductors?

With a velocity so great that the most rapid motion produced by art appears to be actual rest when compared to it. Some authorities have estimated that electricity will pass through copper wire at the rate of two hundred and eighty-eight thousand miles in a second  of time—a velocity greater than that of light.

What agents are undoubtedly the most active in producing and exciting electricity in the operations of nature?

The light  and the sun's rays.

Do some animals have the power of exciting electricity within themselves?

There are  certain animals which are gifted  with the extraordinary power of producing electrical phenomena  by an effort of muscular or nervous energy. Among these the electrical eel and the torpedo are most remarkable.

How powerful a charge of electricity can the electrical eel send forth when in full vigor?

Sufficient to knock down a man or stun a horse.

Is the electricity generated by these animals the same as that occasioned by the ordinary electrical machine?

It is the same, and produces the same effects.

Do vital action and muscular movements in man and animals give rise to electricity?

They do ; and it can be shown by direct experiment that a person cannot even contract the muscles of the arm without exciting an electrical action.

Does change of form or state in bodies generally produce electrical excitation?

Change of form or state is one of the most powerful methods  of exciting electricity.

Water, in passing into steam by artificial heat, or in evaporating by the action of the sun or wind, generates large quantities of electricity. The crystallization of solids from liquids, all changes of temperature, the growth and decay of vegetables, are also instrumental in producing electrical phenomena.