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 authors criticise the statement made by Jaeger and Lindeck, that the variation of manganin resistances with atmospheric humidity need cause no anxiety to the owners of such resistances. In a particular case at the Bureau of Standards the variation of resistance of a standard coil between Jan, 1 and May 1, 1907, was about 85 parts in 100,000, the change occurring in the course of two weeks of damp weather, with the humidity averaging 64 per cent. The atmospheric conditions were not more...

Topics: apparatus and instruments, measurements and use of instruments, Condensed matter, electronic...

The most obvious method of directly determining the inductance of a coil is that originally proposed by Joubert, and consists in first determining the impedance of the coil and then finding the ohmic resistance of the wire and the frequency of the current employed. In a variation of this method, described by Gray, a non-inductive resistance is placed in series with the coil whose inductance is to be measured, and an alternating current passed through both. By means of an electrometer the...

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

Greater sensitiveness is obtained by placing the whole in a vacuum.

Topic: apparatus and instruments/ B7500 Medical physics and biomedical engineering

The authors suggest the use of the name "inductor" for apparatus used to introduce "inductance" into a circuit, as well as "resistor" for apparatus possessing the property of "resistance." The paper describes the method of evolution and construction of an inductor having a range of variation of about 1 millihenry and a current-carrying capacity of about 5 amps. The form of apparatus considered to be most suitable is that consisting of two circular plates...

Topics: apparatus and instruments, Condensed matter, electronic structure, electrical, magnetic, and...

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...

Various methods for measuring capacity, with alternating and direct current, and the advantages and disadvantages of each, are discussed. For this particular investiation the series inductance method was preferred, and was used almot exclusively. There is a wide variation in the temperature-coefficient of mica condensers, and in seeking the cause of this it was observed that of 2 condensers of similar capacity the one with the larger temperature-coefficient was the thicker. In a particular case...

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

Rosa and Babcock have shown that resistance coils kept in an atmosphere of constant humidity are practically constant in resistance. The coil now described is wound in the usual manner on a brass cylinder 3 cm. in diam. and 7 cm. long, and is contained within a cylinder 4 cm. in diam. and 12.5 cm. high. The coil is shellacked, dried, and annealed in the usual manner. It is supported by a small tube closed at the bottom, which serves as a thermometer tube. The hard-rubber top through which the...

Topics: apparatus and instruments, measurements and use of instruments, Condensed matter, electronic...

measurements and use of instruments; General Physics

Topic: USA

Topics: alternating-current research, inductance, Electricity and magnetism, fields and charged particles

Topics: inductance, Electrical instruments and techniques

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

Mathy, by introducing the Weierstrassian notation, obtaines the mutual inductance of two parallel, coaxial circles in terms of hypergeometrical series instead of the usual elliptic functions. The author examines the formula obtained, and finds that it is subject to serious limitations. In many cases its error may be as great as 10 per cent. Before using it a preliminary examination is necessary to see whether the series is uniformly converging or not. A special formula is given when the...

Topics: inductance, Electrical instruments and techniques

The linear thermopile consisting of Bi and Ag wires with rectangular receivers attached to the junctures of these two metals has all the advantages of a good bolometer with none of its disadvantages. Its novelty consists in a series of overlapping receivers forming a continuous surface. The object of the present paper is to illustrate various modifications and uses to which this instrument has been adapted and to indicate further applications. The continuous surface of the receiver has a...

Topics: thermoelectricity, Condensed matter, electronic structure, electrical, magnetic, and optical...

In 1896 Wien described the construction of a convenient and permanent form of inductance standard, the spool being of serpentine. This form of inductance standard has since been manufactured by several of the German instrument makers, and the Bureau of Standards has purchased a considerable number of them. In attempting measurements of high precision on these coils discrepancies were found which were difficult to understand until investigation showed the serpentine to be slightly magnetic and...

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

The Arsem vacuum furnace previously used was slightly modified, and arrangements were made to sweep out the smoke from the heated oxides which affects the optical pyrometer readings. The materials as a rule are charged into the ring space between an outer and an inner tube; some gas (hydrogen, nitrogen, etc.), is passed down the inner tube, into which the pyrometer is sighted. The tubes are made of graphite or of tungsten, the latter being moulded in graphite. The pyrometer lamps were...

Topics: freezing, melting and boiling points, materials properties, Heat flow, thermal and thermodynamic...

For the first time, it is believed, a pyrheliometer has been calibrated by two methods, the usual electrical method and a radiometric method. In the radiometric method a known quantity of radiation from a black body was allowed to fall upon the pyrheliometer receiver in exactly the same manner as when employed for solar measurements. The calibrations by the two methods agreed within limits of experimental error, if the Stefan-Boltzmann constant were chosen as sigma = 5.7*10/sup 12/ watts...

Topics: meteorology, General Physics

It is shown that while the transformation ratio of current transformers usually decreases with increasing current, it may increase in individual cases or even attain a maximum. This ratio and the phase-angle at various loads can be accurately computed from the magnetic data of the core. The slope of the ratio curve can in general be qualitatively predicted from the value of the Steinmetz coefficient. But the iron losses, especially at low flux densities, cannot be accurately- represented by a...

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

In a previous paper the authors deterined the melting-and freezing-points of a number of metals on the temperature scale defined by the Pt-resistace thermometer calibrated in ice, steam, and sulphur vapour (444.70 degrees on the constant-volume notrogen thermometer). In order to throw further light on the probable accuaracy of the temperature scale so defined, in the interval 100 degrees to 500 degrees C, the authors have made some further measurements by the same method on the boiling-points...

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

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,...

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

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

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

A new method is suggested for the absolute measurement of resistance. A revolving coil, or 2 such coils, are to be so disposed in the magnetic field of a pair of fixed coils as to yield an e.m.f. which can be compared, by means of a differential galvanometer, with the fall of potential through a fixed resistance, and so give the absolute value of the resistance. The advantage of this method would be that the e.m.f. generated could be a thousand times greater than in a Lorenz apparatus, while...

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

A study of the various methods of measuring the time-constants of four-terminal resistance standards, which are classified into two main types, viz. (1) those in which the working material is formed into a /b closed/ circuit of as little self-inductance as possible, and the potential leads kept free from all inductive effects, and (2) those in which the potential leads are placed as close as possible to this working resistance so that the mutual inductance of the lead and the resistance is...

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

As a result of the investigation of various liquids for use as standards in the calibration of viscometers of several forms, it is concluded that mixtures of 20, 40, and 60% ethyl alcohol in water (by weight), and solutions of 20, 40, and 60% of surcrose are the most suitable. Tabulated values of the viscosities and fluidities of these liquids from 0 degrees to 100 degrees C. at intervals of 10 deg. C. are given. From the curves of fluidities given it is considered that, owing to their simple...

Topics: viscosity, General Physics

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

In the first part of the paper measurements are given of the radiation from the Hefner lamp and from a standard sperm candle relative to that of a black body. The radiation from these standard sources is given in absolute values on the assumption that the radiation constant is 5.7*10/sup -12/ watt cm./sup 2/ deg./sup -4/, which is practically the mean value of the best present-day determinations. The data are considered to be useful for rough calibrations of radiometers in absolute measure. For...

Topics: rays and radiation, thermometry, pyrometry and calorimetry, Heat flow, thermal and thermodynamic...

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 method used consists in heating a small quantity of the metal whose melting-point is to be observed on a platinum strip through which a current is passed. This is surrounded by a blackened brass tube with a mica window, and the sample is simultaneously watched by two observers through a microscope and an optical pyrometer. In the calibration of the optical pyrometer 1,753 degrees was taken as the Pt melting-point. The correction for absorption and reflection by the mica is about 15 degrees...

Topics: freezing, melting and boiling points, measurements and use of instruments, thermometry, pyrometry...

Modern instrument transformers have such good characteristics that it is not easy to determine their constants by using wattmeters or watt-hour meters in both primary and secondary circuits. The small differences to be measured are masked by errors of measurement, and such a method is not applicable to high voltages or large current-ranges. A modern induction watt-hour meter, however, can be used to determine /b difference/ in ratios and /b difference/ in phase angles between two voltage- or...

Topics: measurements and use of instruments, transformers, rotary converters and boosters/ B8300 Power...

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

A description of electromagnet moving-coil galvanometers for measurements on alternating currents and a presentation of the theory of their action. From the equations of motion of a coil carrying an alternating current in an alternating magnetic field it is shown that the deflection thetas = GE cos [ beta /(RU)], where G is the rate of change with the deflection of the effective value of the flux, E the effective value of the impressed e.m.f., beta the angle of lead of the impressed e.m.f....

Topics: apparatus and instruments, measurements and use of instruments, Condensed matter, electronic...

The authors refer to the use of tungsten filaments in "comparison lamps" such as are employed in series of tests at the Bureau of Standards. A lamp employed in this capacity is run continuously for long periods of time, and it is desirable that the change in candle-power during this time should be as small as possible. The tungsten lamp, when running at about 3 watts per c.p., yields light which matches that of a carbon lamp in colour; when burnt under these conditions lamps were...

Topics: lamps and lighting, photometry/ B8530B Light sources

Describes convenient methods for adjusting the Thomson bridge when very low resistances are measured. The adjustments are made without the repeated opening and closing of the low-resistance connection between the two low-resistance arms.

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

A theoretical discussion is given to show the conditions which must be fulfilled in the construction of resistance coils in order that the phase angle shall be small and the change of resistance with frequency negligible. These principles are applied to the design of coils of different values, and specifications are given for the construction of coils of different denominations from 0.1 to 10,000 ohms.

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

Topics: measurements and use of instruments, Heat flow, thermal and thermodynamic processes

This paper comprises a complete statement of previous formulae and includes the development of a more direct solution of the case where two parallel, coaxial, circular ceils are placed at such a distance that their mutual attraction or repulsion is a maximum. Methods for the application of the formulae, worked-out examples, and tables to facilitate calculation are given. The paper does not permit of a more detailed abstract.

Topics: electricity and magnetism, Condensed matter, electronic structure, electrical, magnetic, and...

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 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...

In magnetic measurements made at the Bureau of Standards it has been found that the heating effect of the current, employed to produce fields of 100 to 300 gauss, changes appreciably the value of the induction for a given field. The usual practice, when an accuracy of 1 % is desired, has been to immerse the coil in an oil bath maintained at a constant temperature of 25 degrees . The object of the present investigation is to determine the magnitude of the temperature effect and to see whether it...

Topics: magnetism, Magnetic properties and materials A4100 Electricity and magnetism, fields and charged...

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 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

specific heat and latent heat; Heat flow, thermal and thermodynamic processes

Topic: USA

[This method was described and put into practice by Blondlot, and the principle was applied to the construction of electricity meters.] The instrument described consists of a relatively large fixed coil with its axis in a horizontal position. At the centre of this fixed coil a movable coil is suspended and the two are concentric when the movable coil is at rest. Attached to the suspended coil is a cylinder of some homogeneous material placed with its axis vertical and coincident with the axis...

Topics: apparatus and instruments, measurements and use of instruments, Electrical instruments and...

A very thorough examination is made of the various formulae which have been proposed from time to time for calculating the mutual inductance of two circular coils of rectangular section. Numerous numerical calculations are made by the various formulae. It is pointed out which are the most accurate and where some of them fail. New formulae are deduced which are more convenient in special cases. Curves are drawn showing the relative accuracy of various formulae for particular coils at varying...

Topics: electromagnetic induction, Electrical instruments and techniques

Describes a new method of determining the focal length of a converging lens by measuring the linear diam. of a circular fringe in the real image formed by the lens. The method makes use of the system of concentric circular fringes obtained by the interference of the light reflected from a partial silver film with that reflected from a heavy polished silver film parallel to the first and behind it, the light being normal to the mirrors. The theory of the method is discussed, and results in a...

Topic: optics

The colorimeter here described is a monochromatic analyser, and was designed to be a practical working instrument of wide range, high precision, and of great simplicity. It is so arranged that light of a pure spectral hue may be mixed with white light to match the unknown; or, in the case of purples, it is mixed with the unknown to match white. The match is made with a photometer cube. In the Fig., collimator 1 is movable; all the remaining parts are fixed. Collimators 1 and 4 with prism P form...

Topic: apparatus and instruments

By slight modifications of the Fabry and Perot procedure of employing interference fringes the author claims to have instituted a more sensitive experimental routine, with consequent improvement in the accuracy of determination of secondary standard wave-lengths. The method is characterised by three chief features: (1) The use of reflection fringes converged by a very short focus lens (20 mm.), thus enabling the disappearances of the bright central spot of the interference rings to be...

Topics: measurements and use of instruments, spectra

This is a continuation of former papers, and consists of (1) an historical summary of the principal determinations up to the present of the value of the constant, sigma , of total radiation; (3) a new determination of by a method in which accurate corrections are made for lack of "blackness" of the radiator, for losses by reflections for variation of thickness of lampblack layer, and for atmospheric absorption. It is demonstrated that the presence of aqueous vapour in unmeasured...

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

In low-resistance standards capable of carrying large currents, the surfaces of the contacts through which the current enters and leaves must be large. In many cases the resistance depends, to some extent, on the manner in which the current leads are attached. In alternating-current measurements it is also necessary to know the inductance. The present paper points out the conditions which must be fulfilled in order that the resistance may be definite, or both the resistance and inductance be...

Topics: measurements and use of instruments, electricity and magnetism, Condensed matter, electronic...

The luminosity of a radiator is defined as the integral from O to infinity with respect to lambda of the product of visibility (V) and energy (J) of the radiating source, /b i,e./ int /sub 0//sup infinity / VJ/b d/ lambda V = /b f/( lambda ) is given by the experimental determinations of Ives, Nutting, and Hyde and Forsythe, and J = /b c/sub 1// lambda /sup -5//b e//sup -c//sub 2//sup lambda thetas / (Wien's law). The effective wave-length lambda L of the luminosity has been defined...

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

One of the most carefully constructed standards of self-inductance in the world was made by Frohlich in 1897. It consists of a large marble ring of rectangular section wound with a single layer of fine silk-covered wire. Frohlich calculated the self-inductance on the assumption that it was the same as for a current sheet the thickness of which was equal to the diam. of the bare wire. He found that L = 0.10199063 henry. The author has previously pointed out that the assumption that a winding of...

Topics: inductance, Electrical instruments and techniques