This paper is an extension and revision of a previous paper by Rosa and Cohen. It is now by far the most complete and thorough study of the subject that has yet been published. The authors have taken great pains to bring it thoroughly up to date, and have made a critical study of nearly all the recent papers on the subject. The comparisons of the results obtained by various authors and the invcstigations of the convergence of the various series that have been proposed have cleared up the whole...

Topics: inductance, Condensed matter, electronic structure, electrical, magnetic, and optical properties

Objection is found to the use of the D lines of sodium as a light source in polariscope measurements, owing to the possible shift in the optical centre of gravity with change of intensity. It is proposed to use the green mercury line ( lambda = 546.1mumu), and the author has measured the temperature-coefficient of the rotatory power of quartz for the D lines and the green mercury line. This will render it possible to compare the observations made with the two sources by different observers.

Topics: measurements and use of instruments, light polarisation

The author finds a new formula for the mutual inductance between a circle and a coaxial helix. J. V. Jones gives two formulae in terms of complete and incomplete elliptic integrals, but making numerical calculations by them is extremely tedious and laborious. The new formula is first deduced from considerations in connection with the potential of a uniformly magnetised circular disc. It is also deduced from a very general formula given by A. Gray [/b Absolute Measurements/, Vol. II., Part I.,...

Topics: electromagnetic induction, measurements and use of instruments, Electrical instruments and...

Interference bands are produced between two optically true glass surfaces in the usual way. Any small movement of one surface relative to the other can be readily seen by the changes in the bands. Several instruments are described; the agents used to change the position of the surfaces, being (1) pressure of a gas, /b e.g./, the pressure produced in a stethoscope by the beating of an artery and communicated to the interference apparatus by a rubber tube; (2) heat produced by an electric current...

Topic: interference

This is the Bureau of Standards reprint of a paper already abstracted together with a section dealing with the behaviour of the Weston cell with rapid temperature changes. In most cases the cells practically attained their normal values within 5 hours after an abrupt change of temperature of over 20 degrees C.

Topics: primary cells, Electricity and magnetism, fields and charged particles

An investigation into the conditions under which, a maximum ratio of intensity to purity may be obtained with spectrum lines. The author gives first a definition of the impurity of a light-source in which every component is weighed according to its intensity. If lambda /sub /b c// be the centre of luminosity and E the intensity of a component of wave-length lambda then- lambda /sub /b c// equiv E/sub 1/ lambda /sub 1/ E/sub 2/ lambda /sub 2/ .../E/sub 1/ E/sub 2/ = int lambda /b d/E/ int /b...

Topic: spectra

It has been shown by Fisher and Austin that the radiation resistance of an antenna decreases rapidly with increasing wave-length to a minimum and then rises again in a linear manner with further increase in wave-length. This increase has been attributed by Austin to dielectric absorption in imperfect dielectrics in the electric field of the antenna. This explanation is verified by the tests now described. An experimental antenna was built in which the bad effects of poor dielectrics in the...

Topic: radiotelegraphy/ B6210 Telecommunication applications

The power of the eye to detect small colour-changes varies, as is known, very far from uniformly throughout the spectrum. The author makes use of Steindler's data on the difference limen and shows how a natural scale can be constructed.

Topics: optics, vision

The author has already referred to the standardisation of the perikon detector, for the same conditions of frequency and coupling, by comparison with a thermo-element. He now makes use of this arrangement, a galvanometer of 2000 ohms' resistance and sensitiveness 1.28*10/sup -9/ amp being used with the dector. In the following table are given the received current and received energy, measured in this way for various sending stations, the measurements being made at the U.S. Naval Wireless...

Topic: radiotelegraphy/ B6210F Telegraphy

Further experiments show that platinum ware in the form of crucibles of whatever degree of purity behaves, with respect to gain or loss of weight, on heating in air at ordinary atmospheric pressure in a manner characteristic only of the temperature of heating. Each impurity, such as Ir, Rh, or Fe, appears to exert its effect on the volatilisation independently, but the loss on heating is negligible below 900 degrees with crucibles of all degrees of purity containing Ir, Rh, Fe, and Si (up to at...

Topics: chemical physics and electro-chemistry, Physical chemistry

A survey of previous researches on the refraction of air shows that many investigators have worked either with white light or with one monochromatic radiation, and dispersion measurements have been limited to a small interval of the spectrum. No index measurements exist for waves longer than those corresponding to orange light, and in the ultra-violet the dispersion formulae disagree by more than 10% of the refractivity. Accordingly it was deemed advisable to measure the absolute indices of...

Topic: light refraction

The two formulae employed by Coffin give results in very close agreement, and the only question remaining is whether the two closely-agreeing formulae are as accurate when applied to the coil in question as they appear to be. In deriving the formulae the current is supposed to be uniformly distributed over the surface of the cylinder, whereas the coil is actually wound with 661 turns of round wire having a diam. of 0.0634 cm. and insulated by a covering 0.0030 cm. thick. The author shows that...

Topics: electromagnetic induction, Electrical instruments and techniques

Gives some applications of the curve of visibility of radiation for the average eye (125 observers) to radiation problems. A mathematical equation is given of the average visibility curve. Using this visibility equation and Planck's equation of the black body, calculations are made of the luminous flux emitted by such a body at various temperatures, also the luminous efficiency, the Crova wave-length, and the mechanical equivalent of light. The visibility curve of the average eye gives the...

Topic: rays and radiation

The initial part of the paper summarises past researches on the pentane lamp. Subsequently general instructions are given for the setting-up and operation of the lamp, and some experiences of the lamps in the United States summarised. A curve is given illustrating change in c.p. caused by varying height of flame, and special emphasis is placed on the avoidance of vitiation of the air, cooling air-currents, etc. Nevertheless it is believed that, with care, the values attained from any lamp can...

Topic: lamps and lighting/ B8530B Light sources

This paper describes a number of measurements of both large and small inductances by Anderson's method, using (1) a battery as a source of current and a d'Arsonval galvanometer, with a rotating commutator to interrupt and reverse simultaneously the current and galvanometer terminals; or (2), what has proved more satisfactory, an alternating-current and a vibration galvanometer, the latter being tuned to the frequency of the current furnished by the generator. The method has been found rapid and...

Topics: measurements and use of instruments, Electrical instruments and techniques

Coffin quoted a formula for the mutual inductance of two coaxial solenoids, which he attributed to Kirchhoff. The author, having found by trial that the formula gave obviously erroneous results, was led to investigate where it was wrong. Using a method suggested by Himstedt, the complete solution of the problem is obtained in terms of complete and incomplete elliptic integrals. The formula agrees with the elliptic integral formula given by Russell, when an algebraical slip in the latter's...

Topics: electromagnetic induction, Electrical instruments and techniques

1. Fraunhofer's A band (wave-length 0.760 mu) and a considerable region of greater wave-length have been photographed in numerous stellar spectra by means of plates sensitised with dicyanin. 2. A strong band at 0.760 mu, nearly coincident with A, has been discovered in spectra of Class M. It is very marked in Mb and Md spectra, and may be useful for purposes of classification. 3. The titanium arc shows flutings near this wave-length, which probably correspond to the stellar bands. 4. In spectra...

Topics: astronomy, photography, General Physics

The effect of annealing a number of thermometers made of Jena 59/sup III/ and 16/sup III/ glasses are tabulated and discussed, the authors pointing out that some of their experiments cover much longer periods of time than those of earlier workers (up to 80 days at temperatures between 400 degrees and 500 degrees C.). The following conclusions of practical importance are arrived at, in addition to detailed results for which the reader must refer to the original: (1) Jena borosilicate 59/sup III/...

Topics: measurements and use of instruments, thermometry, pyrometry and calorimetry, Heat flow, thermal and...

The authors first give a complete proof of Maxwell's formula for the mutual inductance between concentric coaxial solenoids of equal length. They then deduce Roiti's formula very simply by means of Maxwell's equations. The formulae of Gray, Searle, Himstedt, and Cohen are discussed. Cohen's formula is very laborious to evaluate, but it is useful in the special cases where the other formulae converge slowly, and when it is necessary to test their accuracy. The authors point out that Russell has...

Topics: electromagnetic induction, Electrical instruments and techniques

Topics: inductance, Electrical instruments and techniques

This paper is supplementary to previous papers on the subject published by the Bureau of Standards, and brings the list of formulae up to date. Butterworth's series formulae for the calculation of the mutual inductance of two parallel coaxial circles are compared with those given by others, and it is shown that they diminish the labour of computation. Butterworth's formulae for the mutual inductance of parallel eccentric circles are next considered, and various particular cases are given and...

Topics: inductance, Condensed matter, electronic structure, electrical, magnetic, and optical properties

The capacities and phase-differences of 13 commercial paper condensers by different English, French, German, and American makers were measured at temperatures varying from 10 degrees to 35 degrees , and at frequencies lying between 33 and 1000 cycles per sec. The results of these measurements are presented in 26 curves, which show, for each condenser, the change of capacity and phase-difference with change of temperature, and the variation of the capacity and phase-difference with change of...

Topics: measurements and use of instruments, telephony, Telephony

Formulae for the self and mutual inductances of straight wires and rectangles are to be found in various books and papers, but their demonstrations are usually omitted, and approximate formulae are often given as though they were exact. The author derives the expressions very simply from Laplace's formula instead of using Neumann's formula, and thus gives a much better physical view of their meaning. He also deduces some interesting new formulae. The assumption is made that the magnetic field...

Topics: inductance, Condensed matter, electronic structure, electrical, magnetic, and optical properties

After a consideration of the meaning of plastic as compared with viscous flow, the author goes on to describe experiments made to determine the laws governing the former. The different types of viscous and plastic flow are discussed theoretically. In the case of mixtures, according to circumstances the viscosities of the components may be additive, the fluidities may be additive (a special case of this is the suspension of solid in a fluid), or slipping or seepage may take place to modify the...

Topics: elasticity, viscosity, General Physics

The photometry of the high-efficiency gas-filled lamp presents difficulties not yet experienced with other types of lamps. The consumption and candle power are found to vary with the position of the lamp, both being greater with the lamp mounted tip up than when it is mounted tip down; if the lamp be rotated to obtain its mean candle-power it is found that the consumption and candle-power vary with the speed of rotation and that the flickering in the photometer is much greater than when...

Topic: lamps and lighting/ B8530B Light sources

The full paper corresponding to.

Topics: lamps and lighting, photometry/ B8530B Light sources

A revision of a paper published in 1911. The authors state that more recent developments have not materially changed the conclusions then stated, but the present paper gives particulars of many additional measurements, covering in all about 80 pentane lamps. The Vernon Harcourt lamp is stated to have stood the test of use, and remains the most practical flame standard we have. Nevertheless, the results obtained indicate that in its present form the pentane lamp cannot be considered as a...

Topic: photometry

rays and radiation;

Topic: USA

Deals with comparative tests on switchboard voltmeters and ammeters (executed for the American Navy Bureau of Equipment). All American makers were given opportunity to submit instruments, and eight firms sent in 0-160-volt voltmeters and 0-200-amp ammeters (the latter being of the millivoltmeter type with separate shunt). The general appearance of the instruments and of the moving coils is shown in half-tone blocks in the original, but the various results are so stated that they can in no way...

Topics: measurements and use of instruments, electrical engineering/ B8000 Power systems and applications

Platinum black, made by reducing a platinum solution with zinc or alkaline formate and then warming with dilute hydrochloric acid to remove iron, is made the anode of an electrolytic apparatus containing HCl. A divided cell is used, the Pt sheet kathode being contained in a porous pot. The apparatus is so arranged that the solution of chlorplatinic acid, which is specifically heavier than the remainder of the solution, is siphoned off as it is formed. In concentrating the solution so obtained...

Topics: electrolysis, Electrochemistry and electrophoresis

The formulae of Rowland, Rayleigh, and Lyle for the mutual inductance of two coaxial coils of rectangular cross-section take second differentials only into account. The formulae of Weinstein and Stefan, however, take into account differential coefficients higher than the second. Weinstein deduces his formula by starting with Maxwell's expression in elliptic integrals for the mutual inductance of two coaxial circles, differentiating it and carrying the operation to the fourth order of...

Topics: electromagnetic induction, Electrical instruments and techniques

A general description of an improved form of calorimetric resistance thermometer is given, together with some points of interest in connection with its use. The essential features of such a thermometer, to which attention has been given, are enumerated. A difference formula for simplifying calorimetric computations is developed in the paper, and its applicability shown.

Topics: thermometry, pyrometry and calorimetry, Heat flow, thermal and thermodynamic processes

The author first reviews the work dealing with the action of this detector, and then describes experiments made with a view to studying the action of alternating currents of low frequency and to settling some outstanding points which are the subject of controversy. The following appear to be the more important points in the author's summary of conclusions. The detector is capable of detecting a few ten-thousandths of a volt (alternating current of low frequency), and with moderate polarisation...

Topics: oscillations and waves (electric), Electricity and magnetism, fields and charged particles

The authors have adapted (1) the continuous-flow calorimeter, and (2) the vacuum-jacketed (Dewar flask) calorimeter to the determination of specific heats of liquids over a temperature-range of a few degrees in the interval between -35 degrees and 20 degrees , measurement of temperature being made by Pt-resistance thermometers, and heat being supplied electrically and measured accurately by the potentiometer method. By the use of the flow calorimeter an accurate determination of the...

Topics: measurements and use of instruments, specific heat and latent heat, Heat flow, thermal and...

Formulae are obtained for the ratio, regulation, and phase-angle of transformers. By making certain assumptions it is shown that these formulas simplify very considerably, but that their accuracy remains quite sufficient for practical work. The exact definition of the rated current and the rated voltage of a transformer is discussed. For instance, take the case of a 5-kv.a., 2200/110-volt transformer. Three different meanings to this are in common use. In the first we suppose that 2200 volts...

Topic: transformers, rotary converters and boosters/ B8300 Power apparatus and electric machines

The wave-lengths of 55 lines in the neon spectrum have been measured by means of the interferometer. These lines lie in the region lambda 3369 to lambda 8495. The strong lines in the visible region have been observed with great accuracy, the probable error being one part in several millions, or less than one-tenth the width of the line. These strong lines were observed by means of three different pairs of interferometer plates which were each used on several interferometers. The ultra-violet...

Topic: spectra

Values hitherto obtained for the residual inductance of "non-inductive" standards of low resistance have been based upon the calculated inductance of some conductor. The inductances of standards of odd shapes have been obtained by measuring the differences between their phase angle and that of the calculated standard. The methods described by the authors determine the phase angles of low-resistance standards without recourse to computed values. In the first method the sum of the phase...

Topics: measurements and use of instruments, Condensed matter, electronic structure, electrical, magnetic,...

metallography and properties and treatment of metals and alloys; chemical physics and electro-chemistry; Physical chemistry

Topic: USA

In a previous communication the results of an investigation of the constant of spectral radiation of a black body were presented. The position, lambda /sub /b m// of the maximum emission E/sub /b m// was computed by taking the wave-lengths lambda /sub 1/ and lambda /sub 2/, corresponding to equal intensities E lambda /sub 1/ = E lambda /sub 2/, on the assumption that the observed energy curve fits the Planck equation. The equation used in computing lambda /sub /b m// requires a knowledge of the...

Topics: rays and radiation, Heat flow, thermal and thermodynamic processes

The object of the investigation is the determination of the monochromatic emissivity for a wave-length lambda = 0.65 mu, and the total emissivity of iron oxide formed by heating iron in air. Several methods were tried, but the only one giving satisfactory results was that of the "microscopic melts." A small sample of the oxide is placed on a Ni or Pt strip heated electrically. Upon the oxide are placed minute pieces of sodium chloride, sodium sulphate, and gold. At the instant of...

Topics: rays and radiation, Heat flow, thermal and thermodynamic processes

This paper is a continuation of the author's investigation into the spectra of mixed gases, and he finds that the same general laws hold good in the present case as before, namely, that the relative intensity of the spectrum of a gas present in a mixture is increased by increasing the relative amount present, that, other things being equal, in a steady discharge the spectrum of that component of a mixture having greater atomic weight will be brighter, and that in a disruptive or forced...

Topic: spectra

The object of the research was to separate the eddy-current loss in iron from the loss due to magnetic hysteresis, and determine whether the latter varies or is constant when the max. value of the magnetic flux is kept constant while the form of the wave is varied. By the application of Rossler's formula a separation of the losses may be approximately accomplished by measurements of the total losses at two frequencies and the same flux density. In order to obtain accurate results the following...

Topics: measurements and use of instruments, electrical engineering, magnetism/ B8000 Power systems and...

The author presents a lengthy and exhaustive summary of the comparative advantages of four types of instruments : the radio-micrometer, the linear thermopile, the Nichols radiometer, and the bolometer with auxiliary galvanometer. He describes in detail the possible methods of improving the sensitiveness of the radio-micrometer, by reducing the weight of moving parts, changing the period, and placing it in a vacuum. The Rubens thermopile is found to be only about half as sensitive as a...

Topics: measurements and use of instruments, thermometry, pyrometry and calorimetry, Heat flow, thermal and...

The meters experimented on were two Stanley meters (I., II.), a Fort Wayne " K" meter (III.), a General Electric (IV.), and a Siemens and Halske meter (V.). All the meters are single-phase, 60-~; the first four being of American make. They were all tested at full load and unity power-factor. They were tested with sine-shaped current and with a distorted wave current alternately. The distorted wave is given by /b i/ = I sin omega /b t/ (I/4) sin ( omega /b t/ - alpha ). When alpha is...

Topics: measurements and use of instruments, electrical engineering, alternating-current research/ B8000...

The resolving power of objectives may be determined experimentally with simple but sensitive apparatus. Denoting by o the least angular separation between the objects to be clearly separated in the image, o = /b a/ lambda //b r/, where /b a/ is a constant and /b r/ the radius of the lens. It is found that, photographing one half of an uncemented half-tone screen, the constant a varies from 0.50 for an image showing no detail, to 0.90 for an image just free from defects. The theoretical value of...

Topic: optics

measurements and use of instruments; General Physics

Topic: USA

Measurements of the thermal expansion of alpha and of beta brass in compositions such as Muntz metal, naval brass, etc., which normally are in equilibrium are given. Fundamental variations in behaviour as regards thermal expansion at temperatures up to 600 degrees C. were noted, due to the transformation in the beta constituent. Manufacturers of brass never quench 60:40 brasses, and data are given which show the ill effects of quenching. It is found that naval brass and manganese bronze which...

Topic: metallography and properties and treatment of metals and alloys/ B0500 Materials science for...

The specific heat of chemically pure copper between 0 degrees and 50 degrees C. has been redetermined with precision on account of its importance in some determinations of the mechanical equivalent of heat which are being undertaken, the thermal capacity of the copper in these experiments amounting to 1 or 2 % of the whole. A new method is adopted in which 50 m, of copper, wire 2.5 mm. in diam. serves the fourfold function of being the test specimen, the calorimeter itself, the heater, and the...

Topics: specific heat and latent heat, Heat flow, thermal and thermodynamic processes

It is well known that the resistance of the wires is small and that the radiation resistance diminishes rapidly as the wave-length increases. Up to the present no satisfactory theory of ground resistance has been developed. The experimental curves of antenna resistance, on account of the decreasing radiation resistance, fall rapidly at first, as the wave-length is increased, and then, as the wave-length is further increased, remain nearly constant if the ground conditions are good as in the...

Topics: antennas, electric resistance/ B5270 Antennas

A full account giving all details.

Topic: apparatus and instruments/ B8000 Power systems and applications

The arc spectra of iron, cobalt, and nickel were photographed in the red and infra-red regions on plates stained with pinacyanol and dicyanin. A large concave grating was used, and exposures up to 10 hours' duration registered many lines with wave-lengths greater than 10,000 A .U., or 1 mu. In the arc spectrum of iron, 298 lines were measured between the limits lambda 6750 and lambda 10689; 606 lines were measured between lambda 5503 and lambda 11623 in the arc spectrum of Co; and 290 lines...

Topic: spectra

Accurate measurements of wave-lengths and determinations of the characteristics of the emission lines in the spectra of the elements are of importance in spectroscopic analysis, and for the discussion of regularities in spectra. Securing such data about the long waves has been delayed chiefly by the insensitiveness of ordinary photographic plates to the red and adjacent infra-red spectral regions. More extensive use of photographic dyes is important for these spectral investigations. Dicyanin...

Topics: measurements and use of instruments, spectra

It is found that a close approximation to uniformity of magnetic flux along a test rod can be secured by using properly constructed specimens and yokes and properly distributed magnetising coils. The double bar and yoke form of magnetic circuit seems to offer the greatest number of advantages and the fewest disadvantages. The reluctance of the yoke and joints can be kept very small. This is accomplished by having the yokes short and of moderately large cross-section, and making the surface of...

Topics: magnetism, measurements and use of instruments, Magnetic properties and materials A4100 Electricity...

An investigation dealing with the adaptation of the resistance thermometer to calorimetric and other uses for which the ordinary form is not suited. The first part of the paper contains a description of the instrument and its calibration, the second part deals with the determination of the transition-point of sodium sulphate by means of two of the thermometers. The value found by Richard and Wells was 32.888 degrees C.; the redetermination by the authors gave 32.384 degrees .

Topics: thermometry, pyrometry and calorimetry, Heat flow, thermal and thermodynamic processes

apparatus and instruments; Electricity and magnetism; fields and charged particles

Topic: USA

This apparatus is H-shaped with test coils ST spanning the free ends of the H and a magnetising coil M wound on the cross-piece. D and D' are also test coils. SDD'T have the same number of turns and are connected in series and in such a manner that the integrated e.m.f.'s induced in S and D' when a magnetising current is reversed in M are in the same direction but in opposition to those simultaneously induced in D and T. The permeameter is initially adjusted so that when the coils S and T...

Topics: magnetism, measurements and use of instruments/ B8000 Power systems and applications