Condenser (electromagnetism)

“ Now, the more rapid the extinction of magnetism in the core after "break" of the primary circuit, the more rapidly will the lines of force collapse, and the more intense will be the induced current in the secondary coil. The condenser diminishes the period of extinction very greatly, while lengthening the period of magnetization after the "make" of the primary current, and so decreasing the strength of the reverse current. ”

“ In analyzing the astonishingly increased power which the condenser gives to the magnetic effect of a circuit, the first question that arises is how the effect varies with the number of turns, whether it increases indefinitely or reaches a maximum beyond which additional turns have no effect. The answer to this first question is linked to the solution of another, viz, whether the degrees deflection are a direct expression of the measure of the magnetic force or not. ”

“ If now there be any damping of the electric oscillations, the effect of the one condenser on the polarized ray for, say, the first oscillation, may be made equal to that of the other condenser for the second oscillation by such a rotation, and so on. Thus these two condensers become an equivalent "crossed" system, the one compensating completely the effect of the other, even if the electric stresses in each are not the same. This would hold for electric oscillations which produce successive stresses that are in a constant ratio to each other. ”

“ Suppose, then, that S denotes the total current which is capable of generating a magnetic field: since the integral of the magnetic force round any curve is proportional to the electric current which flows through the gap enclosed by the curve, we have in suitable units curl H = 4πS. In order to determine S, we may consider the case of a condenser whose coatings are supplied with electricity by a conduction-current ι per unit-area of coating. ”

“ Electro-magnetic effects are primarily unavailable, for the reason that to produce the required effects we would have to pass current impulses through a conductor, which, long before the required frequency of the impulses could be reached, would cease to transmit them. On the other hand, electro-magnetic waves many times longer than those of light, and producible by sudden discharge of a condenser, could not be utilized, it would seem, except we avail ourselves of their effect upon conductors as in the present methods, which are wasteful. ”

“ In this case it must be assumed that some such process as conduction through the glass takes place, and all the more as it is possible to show by experiment, that with a sufficiently high steady difference of potential, enough current can be passed through the glass of a condenser with mercury coating to light up a Geissler tube joined in series with the condenser. When the potential is alternating, the condenser action comes in and conduction becomes insignificant, and the more so, the greater the rate of alternation or change per unit of time. ”

“ A condenser can hold much more electrification at a certain potential than an equal amount of surface can hold when not properly arranged. We might call a condenser a storage battery for static electricity. The capacity of a condenser depends, among other things, upon the area of the conducting surfaces, and upon the thickness and nature of the dielectric. ”

“ A is an induction coil, supplied with current from the battery B, and C is a condenser. A condenser is simply an apparatus for storing up charges of electricity. It may take a variety of forms, but in every case it must consist of two conducting layers separated by a non-conducting layer, the latter being called the “dielectric.” The Leyden jar is a condenser, with conducting layers of tinfoil and a dielectric of glass, but the condensers used for wireless purposes generally consist of a number of parallel sheets of metal separated by glass or mica, or in some cases by air only. ”

“ That is, the light condenser, the device that stored the photons so close to each other, would also serve to urge them apart. I've made the necessary changes, and now I'm trying to set up the apparatus to work on solid light-mat [Pg. 199] ter. It was developed for gaseous material, and it's a rather tricky thing to change it over. But I think we've almost got it.
“Wade, will you connect that to the high frequency oscillator there—no—through that counterbalanced condenser. We may have to change the oscillator frequency quite a bit, but a variable condenser will do that. ”

“ The capacity of a condenser may be ascertained in electromagnetic measure by a comparison of the electromotive force which produces the charge, and the quantity of electricity in the current of discharge. By means of a voltaic battery a current is maintained through a circuit containing a coil of great resistance. The condenser is charged by putting its electrodes in contact with those of che resistance coil. The current through the coil is measured by the deflexion which it produces in a galvanometer. ”

“ The postscript begins by referring to the “condenser [Kondensator] just brought to my attention by Herr Poggendorf” and explains that he cannot release his treatise “without preliminary announcement of this subject of the highest importance.” (It can be inferred from the text that the name “condenser” was chosen because of the device’s enhancing of magnetic measurements analogously to the enhancing of electric measurements by Volta’s electrostatic “condenser.”) ”

“ Now let the condenser be discharged by connecting the extreme surfaces through a perfect conductor so that their potentials are instantly rendered equal, then the electricity on the extreme surfaces will be altered, but that on the internal surfaces will not have time to escape. ”

“ Each refuses to escape to the earth, but they instantly rush together at the first opportunity. The dielectric may be shattered in a very heavily-charged condenser by this strong attraction.
Fig. 55.
EXPERIMENT 89. To show how the condenser maybe slowly discharged.
Apparatus. Fig. 55. The condenser (Exp. 83) ; the carbon electroscope with support (Exp. 58) ; the electrophorus (Exp. 68) .
192. Directions. (A) Charge the condenser by means of the [74] electrophorus; then hang the carbon so that it can swing between the upper conductor and E C placed as shown. ”

“ Now there is only one method by which currents of high frequency, or radio-frequency, as they are termed, can be set up by spark transmitters, and this is by discharging a charged condenser through a circuit having a small resistance. To charge a condenser a spark coil or a transformer is used and the ends of the secondary coil, which delivers the high potential alternating current, are connected with the condenser. To discharge the condenser automatically a spark, or an arc, or the flow of electrons in a vacuum tube, is employed. ”

“ Nor should it be thought that the temperature of an air condenser would give even an approximate idea of the loss in heat incurred, as in such case heat must be given off much more quickly, since there is, in addition to the ordinary radiation, a very active carrying away of heat by independent carriers going on, and since not only the apparatus, but the air at some distance from it is heated in consequence of the collisions which must occur. ”

“ The potential difference across the latter is therefore instantly increased, tending to further charge the condenser. This increase of charge reacts on the arc, increasing its current. The condenser discharges, through the inductance coil, and becomes charged in the opposite direction, just like a spring, which released, goes beyond its normal position and then returns.
The operation is repeated many times per second (usually over 1,000,000) , setting up persistent undamped oscillations. ”

“ Sir David Brewster says that the bodies to be evaporated or dissolved were placed upon an insulating stand and were made to communicate by a chain or wire with a Cavallo electrometer, or with Volta’s condenser, when it was suspected that the electricity increased gradually. When sulphuric acid, diluted with three parts of water, was poured upon iron filings, inflammable air was disengaged with a brisk effervescence; and, at the end of a few minutes, the condenser was so highly charged as to yield a strong spark of negative electricity. ”

“ We shall take the case of a condenser composed of any number of parallel layers of different materials. If a constant difference of potentials between its extreme surfaces is kept up for a sufficient time till a condition of permanent steady flow of electricity is established, then each bounding surface will have a charge of electricity depending on the nature of the substances on each side of it. ”

“ In connection with machines of such high frequencies, the condenser affords an especially interesting study. It is easy to raise the electromotive force of such a machine to four or five times the value by simply connecting the condenser to the circuit, and the writer has continually used the condenser for the purposes of regulation, as suggested by Blakesley in his book on alternate currents, in which he has treated the most frequently occurring condenser problems with exquisite simplicity and clearness. ”

“ The employment of an intense magnetic field is of advantage principally when the induction coil or transformer which charges the condenser is operated by currents of very low frequency. In such a case the number of the fundamental discharges between the knobs may be so small as to render the currents produced in the secondary unsuitable for many experiments. The intense magnetic field then serves to blow out the arc between the knobs as soon as it is formed, and the fundamental discharges occur in quicker succession. ”

“ The insulating qualities of air are reduced by heating of the condenser plates and by reductions in the air pressure. If the plates are put in a vacuum, there is practically no dielectric between them.
In speaking of the vanishing metal, I think Kathis Kathkan referred to the light tinfoil in a condenser which is sometimes eaten away by the brushing of too high a voltage. Copper, brass, or aluminum will not eat away like the foil. ”

“ If the wire of a battery-circuit be broken at any point, and the broken ends connected with the electrodes of a condenser, the current will flow into the condenser with a strength which diminishes as the difference of the potentials of the condenser increases, so that when the condenser has received the full charge corresponding to the electromotive force acting on the wire the current ceases entirely. ”

“ We may here remark that any arrangement of two metallic plates with a sheet of insulator or non-conductor between them is called a condenser. Thus, a condenser can be built up by coating a sheeting of glass on its two sides with tinfoil, or in place of glass we may use mica, paraffin paper, or any other good non-conductor. We may even use air at ordinary pressures; and thus, if two metal plates are placed near to one another in air, the plates being both insulated—that is, supported on non-conductors,—this arrangement constitutes what is called an air condenser. ”