The old farm house had been wrapped in insulation and sided.
Unless the insulation is perfect, the potential recorded falls short of that at the spot where the radium is placed or the water jet breaks.
The potentials that have to be dealt with are often hundreds and sometimes thousands of volts, and insulation troubles are more serious than is generally appreciated.
The great advantage of this air insulation is that the electrostatic capacity of the wires is low (about one-third of that which would be obtained with gutta-percha insulation), which is of the utmost importance for high-speed working or for longdistance telephonic communication.
The one disadvantage of paper cables is the fact that any injury to the lead covering which allows moisture to penetrate causes telegraphic interruption to the whole of the enclosed wires, whereas if the wires are each individually coated with gutta-percha, the presence of moisture can only affect those wires whose covering is defective There is no reason for doubting, however, that, provided the lead covering remains intact, the paper insulation is imperishable; this is not the case with gutta-percha-covered wires.
The galvanometer being so adjusted that a current of definite strength through one of the coils gives a definite deflection of the needle, the amount of leakage expressed in terms of the insulation resistance of the wires is given by the formula.
Total insulation resistance of looped lines = 2 R(D/d - 1); in which R is the total resistance of the looped wires, including the resistance of the two coils of the galvanometer, of the battery, and of the two resistance coils r and r' (inserted for the purpose of causing the leakage on the lines to have a maximum effect on the galvanometer.
For the purpose of avoiding calculation, tables are provided showing the values of the total insulation according to the formula, corresponding to various values of d.
The climatic conditions in the British Islands are such that it is not possible to maintain, in unfavourable weather, a higher standard than that named, which is the insulation obtained when all the insulators are in perfect condition and only the normal leakage, due to moisture, is present.
The insulation is again tested, and if no fault is discovered the served core is passed through the sheathing machine, and the iron sheath and the outer covering are laid on.
In this way communication was established from both sides on the 16th of August, but it did not continue long, for the insulation had been ruined by Whitehouse's treatment, and after the 20th of October no signals could be got through.
In the types of cable that were first used, the wires, usually with a cotton insulation, were drawn into lead tubes, and the tubes filled with paraffin or other similar compound, which kept the wires from the injurious effects of any moisture which might penetrate the lead tube.
Oliver Heaviside showed mathematically that uniformly-distributed inductance in a telephone line would diminish both attenuation and distortion, and that if the inductance were great enough and the insulation resistance not too high the circuit would be distortionless, while currents of all frequencies would be equally attenuated.
(4) Expansion or compression under the condition of heat-insulation, represented by curves called Adiabatics, such as BAZ or CDZ', which are necessarily steeper than the isothermals.
The last elaboration of the insulated slip water-bottle by Ekman, Nansen and Pettersson has produced an instrument of great perfection, in which the insulation is effected by layers of water between a series of concentric ebonite cylinders, all of which are closed both above and below when the apparatus encloses a sample, and each of which in turn must be warmed considerably before there is any rise of temperature in the chamber within.
OHMMETER, an electrical instrument employed for measuring insulation-resistance or other high electrical resistances.
Suppose it is desired to measure the insulation-resistance of a system of electric house wiring; the ohmmeter circuits are then joined up as shown in fig.
On setting the dynamo in operation, a current passes through the shunt coil of the ohmmeter proportional to the voltage of the dynamo, and, if there is any sensible leakage through the insulator to earth, at the same time another current passes through the series coil proportional to the conductivity of the insulation of the wiring under the electromotive force used.
Hence the deflection of the needle is proportional to the insulation resistance, and the scale can be graduated to show directly this resistance in megohms.
The Evershed and Vignoles form of the instrument is much used in testing the insulation resistance of electric wiring in houses.
One of these coils is in series with the armature circuit and with the insulation or high resistance to be measured.
Of the ends of the insulator and the current flowing through it, that is, by its insulation resistance.
In this case one terminal of the battery is connected to the earth, and the other terminal is connected through the galvanometer with the copper wire, the insulation of which it is desired to test.
When the price of aluminium is less than double the price of copper aluminium is cheaper than copper per unit of electric current conveyed; but when insulation is necessary, the smaller size of the copper wire renders it more economical.
In 1140 a Benedictine monastery was founded here by Ralph Boteler of Oversley, and received the name of the Church of Our Lady of the Isle, owing to its insulation by a moat meeting the river Arrow.
This insulation, however, is not sufficiently good for an electroscope intended for the detection of radio-activity; for this purpose .:..................... ?,:.?