scholarly journals II. On the specific resistance of mercury

1883 ◽  
Vol 174 ◽  
pp. 173-185 ◽  
Keyword(s):  
Present State ◽  
Electrical Resistance ◽  
Specific Resistance ◽  
British Association ◽  
Absolute Measure ◽  
The Subject ◽  
Absolute Measurements

Our experiments on the determination of the British Association unit of electrical resistance in absolute measure are detailed in two memoirs communicated to the Society. The conclusion to which they led us is that 1 B. A. unit=·9865 earth quadrant / second, but this result differs considerably from that obtained by some other experimenters, the original Committee included. Although in the present state of the question it is not desirable that the B. A. unit should fall into disuse, there can be no question as to the importance of connecting it with the mercury unit introduced now more than twenty years ago by Siemens. It will then be possible, as recommended by the Paris Conference, to express our absolute measurements in terms of mercury, by stating what length of a column of mercury at 0° of 1 square millimetre section has a resistance of 1 ohm. Accordingly the experiments about to be described relate to the expression in terms of the B. A. unit of the resistances of known columns of mercury at 0°. This investigation was the more necessary, as the principal authorities on the subject, Dr. Werner Siemens and Dr. Matthiessen, had obtained results differing by as much as ·8 per cent.

scholarly journals XIX.—Magnetization and Resistance of Nickel Wire at High Temperatures. Part II.

1907 ◽  
Vol 45 (3) ◽  
pp. 547-554
Author(s):  
C. G. Knott
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Electrical Resistance ◽  
British Association ◽  
Nickel Wire ◽  
Present Communication ◽  
Association Meeting ◽  
The Subject ◽  
The Wire

The experiments which form the subject of the present communication were carried out two years ago, and supplement results already published. A brief note of some of the results was read before the Society in June 1904, and was also read before the British Association Meeting at Cambridge in August of the same year.The previous paper discussed the effect of high temperature on the relation between electrical resistance and magnetization when the wire was magnetized longitudinally, that is, in the direction in which the resistance was measured.The present results have to do with the effect of high temperature on the relation between resistance and magnetization when the magnetization was transverse to the direction along which the resistance was measured.

scholarly journals I. On the determination of the specific resistance of mercury in absolute measure

1891 ◽  
Vol 182 ◽  
pp. 1-42 ◽  
Keyword(s):  
Specific Resistance ◽  
Cavendish Laboratory ◽  
Philosophical Magazine ◽  
Adequate Response ◽  
Absolute Measure ◽  
The One ◽  
Prospect Of Success

“ On the whole I am of opinion that if it is desirable at the present time to construct apparatus on the most favourable scale, so as to reach the highest attain­ able accuracy, the modification of Lorenz’s method last described is the one that offers the best prospect of success. Before this is done however, it appears to me important that the value now three times obtained in the Cavendish Laboratory by distinct methods should be approximately verified (or disproved) by other physicists. To distinguish between this value and those obtained for instance by Kohlrausch, by Lorenz, or by the First B. A. Committee, should not require the construction of unusually costly apparatus. Until the larger question is disposed of it appears premature to discuss the details of arrangements from which the highest degree of precision is to be expected.” The above passage, which concludes a paper communicated by Lord Rayleigh to the ‘Philosophical Magazine, a little before the Electrical Congress at Paris, at which the legal ohm was defined to be the resistance of a column of mercury of 1 sq. mm. section and 1060 mm. long, seems not to have met with adequate response in this country. So far as experiments in English Laboratories are concerned the determination of the ohm remains where Lord Rayleigh left it, except for the contribution made by Glazebrook and Fitzpatrick in their re-measurement of the Specific Resistance of Mercury in terms of the B. A. Unit, which is one of the elements in the determination of the Specific Resistance of Mercury in Absolute Measure by Lord Rayleigh’s adaptation of Lorenz’s method.

XIII. Experiments to determine the value of the British association unit of resistance in absolute measure

1882 ◽  
Vol 173 ◽  
pp. 661-697 ◽  
Keyword(s):  
Relative Velocity ◽  
British Association ◽  
Great Weight ◽  
Electric Currents ◽  
Sliding Surfaces ◽  
General Plan ◽  
Linear Dimensions ◽  
Absolute Measure ◽  
New Apparatus

The present paper relates to the same subject as that entitled “On the Determination of the Ohm in Absolute Measure," communicated to the Society by Dr. Schuster and myself, and published in the Proceedings for April 12, 1881 —referred to in the sequel as the former paper. The title has been altered to bring it into agreement with the resolutions of the Paris Electrical Congress, who decided that the ohm was to mean in future the absolute unit (10 9 C. G. S.), and not, as has usually been the intention, the unit issued by the Committee of the British Association, called for brevity the B.A. unit. Much that was said in the former paper applies equally to the present experiments, and will not in general be repeated, except for correction or additional emphasis. The new apparatus (Plate 48) was constructed by Messrs. Elliott on the same general plan as that employed by the original Committee, the principal difference being an enlargement of the linear dimensions in the ratio of about 3 : 2. The frame by which the revolving parts are supported is provided with insulating pieces to prevent the formation of induced electric currents, and more space is allowed than before between the frame and those parts of the ring which most nearly approach it during the revolution. It is supported on three levelling screws, and is clamped by bolts and nuts to the stone table upon which it stands. The ring is firmly fastened by nuts to two gun-metal pieces which penetrate it at the ends of the vertical diameter, and which form the shaft on which it rotates. The lower end of the bottom piece is rounded, and bears upon a plate of agate, on which the weight of the revolving parts is taken. A little above this comes the driving pulley (9 inches in diameter), and above this again the screw and nut by which the divided card is held. The top piece is hollow, forming a tube with an aperture of 1¼ inches, and is held by a well-fitting brass collar attached to the upper part of the frame. On this bearing the force is very small, so that the considerable relative velocity of the sliding surfaces has no ill effect. Notwithstanding its great weight, the ring ran very lightly, and the principal resistance to be overcome was that due to setting air in motion.

scholarly journals I. On a standard voltaic battery

1874 ◽  
Vol 164 ◽  
pp. 1-14 ◽  
Keyword(s):  
Electric Potential ◽  
Electrical Resistance ◽  
Electromotive Force ◽  
Electrical Measurement ◽  
British Association ◽  
Recent History ◽  
History Of ◽  
William Thomson ◽  
The Subject ◽  
Mutual Relations

The object which the author had in view in pursuing the investigations alluded to in the following paper was to discover some form of voltaic battery which should have a perfectly constant electromotive force, and should maintain a uniform difference of electric potential between its poles. This want has been much felt by electricians; and the utility of such an investigation may be best shown by a brief reference to the recent history of electrical measurement. In September 1861 a paper was read by the author before the British Association for the Advancement of Science advocating the adoption of a series of standard units of electrical measurement, and pointing out the mutual relations which should exist between such units. The subject was independently supported in Committee by Sir William Thomson, F. R. S., and the result was the appointment of a “ Committee on Standards of Electrical Resistance,” and a grant of money was set aside for the purposes of the Committee.

I. On the determination of the specific resistance of mercury in absolute measure

1891 ◽  
Vol 48 (292-295) ◽  
pp. 434-437
Keyword(s):  
Specific Resistance ◽  
Accurate Determination ◽  
Considerable Time ◽  
Absolute Measure ◽  
University College ◽  
Complete Sets ◽  
The University ◽  
Made In ◽  
The Way

In the hope of paving the way for a more accurate determination of the ohm, the author has for a considerable time been engaged in submitting to the test of experiment certain modifications of the method of Lorenz which occurred to him as likely to lead to increased accuracy and certainty. The experiments have been made in the laboratory of the University College, Cardiff, with apparatus for the most part constructed in the College workshop. Five complete sets of observations were taken in the spring of this year, with the following results for the specific resistance of mercury at 0ºC.

scholarly journals On the electrical resistance of moving matter

1908 ◽  
Vol 80 (540) ◽  
pp. 420-435 ◽  
Keyword(s):  
Relative Motion ◽  
Electrical Resistance ◽  
Specific Resistance ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Direction Parallel ◽  
The Earth ◽  
The Subject ◽  
Actual Method

The question of relative motion between the earth and the neighbouring ether has been under discussion for many years. It has, from time to time, been the subject of important investigations; but these have all resulted negatively. The experiment about to be described is not different from them in this respect, yielding, as it does, no definite information on the main point. It was suggested and commenced by one of us some years ago; but the serious difficulties which invariably attend measurements of such delicacy have delayed its completion till the present time. Indirectly, the aim was to measure the direction and magnitude of etherdrift; the actual method having been to attempt to demonstrate the existence of the Fitzgerald-Lorentz shrinkage which has been supposed to mask the effect in the direct experiments of Michelson and Morley, and of Trouton and Noble. It may be as well to say at once that if such a shrinkage be real, it is in this experiment also obscured by some other exactly compensating change or changes, no effect approaching that to be otherwise expected having been observed. The principle of the measurement is a very simple one. Imagine a uniform wire AB (fig. 1) of length l and cross-sectional area a moving through the ether in a direction parallel to its length with a velocity v . Let ρ be its specific resistance and R its total electrical resistance. The relation R = ρ l / a is then true. Differentiating logarithmically, we obtain δR/R = δ ρ / ρ +δ l / l -δ a / a .

scholarly journals XII. Determination of verdet’s constant in absolute units

1877 ◽  
Vol 25 (171-178) ◽  
pp. 144-147
Keyword(s):  
Magnetic Force ◽  
Polarized Light ◽  
Absolute Measure ◽  
The Subject

In the year 1845 Faraday discovered that if plane polarized light passes through certain media, and these media be acted on by a sufficiently powerful magnetic force, the plane of polarization is rotated. About the year 1853 M. Verdet commenced a long and exhaustive examination of the subject, and his first result (published ‘Ann. de Chimie et de Phys.’ 3 série, tom. xli.) was that, for any given magnet and medium, “the ratio between the strength of the magnet and the amount of rotation is constant”. The object of the present research is to determine this constant in absolute measure—that is, in the C. G. S. system.

scholarly journals XVII. On the influence of temperature on the refraction of light

1859 ◽  
Vol 9 ◽  
pp. 328-331
Keyword(s):  
British Association ◽  
Refractive Indices ◽  
Temperature Influence ◽  
Influence Of Temperature ◽  
Influence Of Temperature On ◽  
The Subject

Those who have occupied themselves with the determination of refractive indices, must have noticed that changes of temperature influence the amount of refraction; yet few of the observations on record have affixed to them the temperature at which they were made, and few, if any, numerical researches have been published on the subject. To determine, if possible, the amount and character of this effect of heat was the object of the present inquiry. The instrument employed was that described by the Rev. Baden Powell in the British Association Report for 1839, and was kindly lent by him for the purpose. The substances more or less fully examined, were bisulphide of carbon, water, ether, methylic, vinic, amylic, and caprylic alcohols, the two principal constituents of creasote—hydrate of phenyle and hydrate of cresyle, phosphorus, oil cassia, and camphor dissolved in alcohol.

The structure of haemoglobin

1952 ◽  
Vol 213 (1115) ◽  
pp. 425-435 ◽  
Keyword(s):  
Direct Method ◽  
Direct Determination ◽  
Subsequent Paper ◽  
X Ray ◽  
The Subject ◽  
Absolute Measurements ◽  
Crystalline Forms ◽  
A Direct Method ◽  
Haemoglobin Molecule

The paper describes the first steps in an attempt to solve the structure of a haemoglobin molecule by X-ray analysis, using a direct method. It is based on an extensive series of absolute measurements of the diffraction by various shrinkage stages of a haemoglobin crystal, and estimates based on many crystalline forms of the general dimensions of the haemoglobin molecule. The methods used are described here and applied to a direct determination of the electron density in one particular direction in the molecule. The extension of the methods to the subsequent problem of obtaining a picture of the molecule as projected on a plane will, it is hoped, form the subject of a subsequent paper.

scholarly journals DESIGN AND CONSTRUCTION OF GROINS

2010 ◽  
Vol 1 (1) ◽  
pp. 27
Author(s):  
Donald F. Horton
Keyword(s):  
Present State ◽  
Current Practice ◽  
State Of The Art ◽  
Beach Erosion ◽  
Shore Protection ◽  
Proper Design ◽  
The Subject ◽  
Design And Construction

Groins are frequently used for shore protection and improvement. Not infrequently the owner of shore property who has had groins built to protect or improve his property is disappointed with the results. More often than not this unhappy situation must be attributed to the fact that too much was expected by the owner. The owner in such a case is not properly to be criticized, because a great deal remains to be learned about groins; their effects, their proper design and construction. In the present state of the art of shore protection and improvement it is not possible to design and build groins without facing numerous uncertainties, particularly in the area of advance determination of the results which will be accomplished. This condition is faced frankly at the very beginning of this paper and should be kept in mind throughout the consideration of the subject of groin design and construction. This paper presents a digest of what is considered by the writer to be the best current practice. No pretense is made for the development of original ideas on the subject. The writer is indebted to many engineers who have contributed accounts of their experiences to the literature, and to the members of the Beach Erosion Board and its staff, especially Dr. Martin A. Mason.

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