If the difference of potential between the terminals is raised, the dielectric breaks down.
In a condenser, for instance, as long as only a solid or only a liquid dielectric is used, the loss is small; but if a gas under ordinary or small pressure be present the loss may be very great.
Perhaps it is because the dielectric losses in the liquid are smaller.
The size of the plates in oil is, however, calculable, as the dielectric losses are very small.
As the current runs in at one side and out at the other, the dielectric becomes charged, and tries to discharge itself by setting up an opposing electric pressure.
The capacity of a condenser is also proportional to the specific inductive capacity of the dielectric between the plates of the condenser.
The number indicating the magnitude of this property of the medium is called its specific inductive capacity, or dielectric constant.
In underground cables for very high pressures, the insulation, if homogeneous throughout, would have to be of very great thickness in order to have sufficient dielectric strength.
The loss is principally due to a phenomenon known as dielectric hysteresis, which is somewhat analogous to magnetic hysteresis.
Duhem has shown, would be propagated in dielectric media with a speed equal to that of light.
The index of refraction of these substances tends in the case of great wave-lengths to become, as the theory anticipates, nearly the square root of the dielectric constant.
Faraday made, in some sort, an equivalent discovery when he perceived that the electrical energy belongs, not to the coatings of the condenser, but to the dielectric which separates them.
For the pitch or resin may be substituted a sheet of glass, ebonite, india-rubber or any other good dielectric placed upon a metallic sheet, called the sole-plate.
To use the apparatus the surface of the dielectric is rubbed with a piece of warm flannel, silk or catskin, so as to electrify it, and the upper metal plate is then placed upon it.
Owing to the irregularities in the surfaces of the dielectric and upper plate the two are only in contact at a few points, and owing to the insulating quality of the dielectric its surface electrical charge cannot move over it.
Maxwell started with the conception that all electric and magnetic phenomena are due to effects taking place in the dielectric or in the ether if the space be vacuous.
At the time when Maxwell developed his theory the dielectric constants of only a few transparent insulators were known and these were for the most part measured with steady or unidirectional electromotive force.
Taking thedielectric constant of air as unity he obtained the following values, for shellac K = 2.
The Dielectric Constants of Certain Organic Bodies at and below the Temperature of Liquid Air," id.
If the dielectricor separating insulator has a constant K, then the capacity becomes K times as great.
S 327, who shows that a composite or stratified dielectric composed of layers of materials of different dielectric constants and resistivities would exhibit the property of residual charge.
On the Dielectric Constants of Metallic Oxides dissolved or suspended in Ice cooled to the Temperature of Liquid Air," id.
We must, however, assume that the charge Q is so small that it does not sensibly disturb the original electric field, and that the dielectric constant of the insulator is unity.
For constant charges and distances the mechanical force is inversely as the dielectric constant.
Note on the Dielectric Constant of Ice and Alcohol at very low Temperatures," ib.
This gave the dielectricconstant K of the material.
Further Observations on the Dielectric Constants of Frozen Electrolytes at and above the Temperature of Liquid Air," id.
We are here arrived at a very simple fact, which clearly shows us the significance of the number called dielectric constant, or specific inductive capacity, the knowledge of which is so important for the theory of submarine cables.
Footnote 30: Making allowance for the corrections indicated in the preceding footnote, I have obtained for the dielectric constant of sulphur the number 3.
For the highest attainable precision one should by rights immerse the two plates of the condenser first wholly in air and then wholly in sulphur, if the ratio of the capacities is to correspond to the dielectric constant.
As the dielectric for such a condenser, only two materials seem to be of any practical use, viz.
In the original form of simple Marconi aerial, the aerial itself when insulated forms one coating or surface of a condenser, the dielectric being the air and ether around it, and the other conductor being the earth.
We have to consider in connection with this part of the subject the dielectric strength of air under different pressures and for different thicknesses.
But whatever advantage may accrue from using oil as thedielectric in which the spark discharge takes place, when carrying out simple laboratory experiments on Hertzian waves, there is no advantage in the case of wireless telegraphy.
The wire has capacity with respect to the earth, and it acts like the inner coating of a Leyden jar, of which the dielectric is the air and ether around it, and the outer coating is the earth's surface.
It was shown by Lord Kelvin, in 1860, that the dielectric strength of very thin layers of air is greater than that of thick layers.
The dielectric should vary enormously in resistance by minute variations of the E.
Hence it was thought that a liquid insulator might be more suitable as a dielectric than air.
It was found, as already stated, that gaseous matter must be most carefully excluded from any dielectric which is subjected to great, rapidly changing electrostatic stresses.
When a solid dielectric is used, it matters little how thick and how good it is; if air be present, streamers form, which gradually heat the dielectric and impair its insulating power, and the discharge finally breaks through.
That is the reason why the rate of change is very much greater when glass, for instance, is broken through, than when the break takes place through an air space of equivalent dielectric strength.
Light will not travel along a conductor, although it is true that the longer waves will be transmitted through a waveguide made of dielectric that is transparent to them.
This state is represented by a vector D ("dielectric displacement") whose magnitude is measured by the quantity of electricity reckoned per unit area which has traversed an element of surface perpendicular to D itself.
Paraffin oil or any liquid dielectric of constant inductivity may replace the air.
Letting go the spring is analogous to permitting a discharge of the jar--permitting the strained dielectric to recover itself--the electrostatic disturbance to subside.
The electrical resistance is about that of ordinary glass, and is diminished by one-half during exposure by Rontgen rays; the dielectric constant (16) is greater than that which should correspond to the specific gravity.
In a dielectric which heats, there may be three kinds of conduction, viz.
The first difficulty is insulation, for the dielectric must be very thin, else the volume of the condenser is too great.
In a transparentdielectric the conduction must be either electrolytic or disruptive, otherwise light vibrations would be damped.
Thompson asked if Mr. Swinburne had found anydielectric which had no absorption.
The sign of the electric charge on the particles of a sol may be either negative or positive, depending upon the chemical nature and dielectric constants of the two phases of the system.
Water, likewise, has a higher dielectric constant than any other common liquid.
It soon appeared to Faraday that the nature of the dielectrichad very much to do with electric induction.
The capacity of a condenser, for instance, depends on the nature of the dielectric as well as on the configuration of the conductors.
In the case of dielectric conductors and of electrolytes, the action of rising temperature is to reduce resistivity.
It is customary in electro-technical work to consider the resistivity of the dielectric as the value it has after the electromotive force has been applied for one minute, the standard temperature being 75 deg.
In good enamel wire the insulation will average about one-quarter the thickness of the standard single silk insulation, and the dielectric strength is equal or greater.
We see then that the capacity of a condenser varies as the area of its plates, as the specific inductive capacity of the dielectric employed, and also inversely as the distance between the plates.
Obviously, when placed in a circuit a condenser offers a complete barrier to the flow of direct current, since no conducting path exists between its terminals, the dielectric offering a very high insulation resistance.
The dielectric strength of enamel insulation is much greater than that of either silk or cotton insulation of equal thickness.
The arrangement of carbons and dielectric in this device is shown in Fig.
S = Shunt leakage in mhos The quantity S is a measure of the combined direct-current conductance (reciprocal of insulation resistance) and the apparent conductance due to dielectric hysteresis.
Mossotti found a relation between the dielectric constant and the space actually occupied by the molecules, viz.
I wrote my thesis on the theory ofdielectric polarization and since then--no, that's classified.
You see, the dielectric constant of this material isn't constant at all.
A practicaldielectric has to be stable in every way, at least over the range of conditions you intend to use it in.
What was really important was the sort of condensers made possible by a genuinely good dielectric material.
The bottoms should be next to the glass, which is used for the dielectric on account of its stiffness.
A good dielectric is said to have a high inductive power or capacity.
The dielectric may be shattered in a very heavily-charged condenser by this strong attraction.
The two electrifications on the opposite sides of the dielectric have such an attraction for each other, when the condenser is charged, that they seem to penetrate, or soak into, the dielectric.
The conductors allow an even and rapid discharge from all parts of the dielectric at the same time.
Such a combination, 2 conductors, with a dielectric between them, is called a condenser.
Condensers may be made in many ways, but they all consist of 2 conductors, with a dielectricbetween them.
Glass is about 3 times as good a dielectric as dry air; and as the latter (under certain conditions) is taken as the standard, or as unity, we may say that the specific inductive capacity of glass is about 3.
The dielectric is considerably strained when a condenser is heavily charged.
It is a mechanical result; and as the liquid passes from the positive towards the negative electrode in all the known cases, it seems to establish a relation to the polar condition of the dielectric in which the current exists (1164.
Another point is the facilitation of electrolytic conducting power or discharge by the addition of substances to the dielectric employed.
The moment of discharge is probably determined by that molecule of the dielectric which, from the circumstances, has its tension most quickly raised up to the maximum intensity.
But introduce such a dielectric as sulphur or lac, into the space between the two conductors on one side only, or opposite one part of the inner sphere, and immediately the electricity on the latter is diffused unequally (1229.
Flame facilitates the production of a current in the dielectric surrounding it.
It of itself brings the contiguous particles of the dielectric into a certain condition, which, if retained by them, constitutes insulation, but if lowered by the communication of power from one particle to another, constitutes conduction.
Letting go the spring is analogous to permitting a discharge of the jar--permitting the strained dielectric to recover itself, the electrostatic disturbance to subside.
Maxwell assumes that if in a dielectric the electric field happens to vary, this dielectric becomes the seat of a particular phenomenon, acting on the galvanometer like a current, and which he calls current of displacement.
Take as example the chapter in which he explains electrostatic attractions by pressures and tensions in the dielectric medium.
An important quantitative relation between the solubility of a given ionogen in different solvents and the ionizing powers of the solvents, as determined by their dielectric constants (p.
In solvents, then, of high dielectric powers, the coëxistence of oppositely charged particles must be more favored than in solvents of low dielectric powers.
Smale, in Nernst's laboratory, on the other hand, obtained results indicating that salt solutions have decidedly higher dielectric constants than pure water.
It is possible, therefore, that the presence of salts in the solution increases the dielectric or, at any rate, the ionizing power of the solvent and there are many facts which would be explained by such a behavior.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "dielectric" in a variety of sentences. We hope that you will now be able to make sentences using this word. Other words: conductance; conduction; conductor; dielectric
