scholarly journals XI. A determination of the specific heat of water in terms of the international electric units

1895 ◽  
Vol 186 ◽  
pp. 415-467 ◽  
Keyword(s):  
Specific Heat ◽  
Electromotive Force ◽  
Good Deal ◽  
Great Accuracy ◽  
Important Research ◽  
Science And Art ◽  
The Wire ◽  
The Difference ◽  
Work Done

This research was originally undertaken by Professor Schuster and Mr. H. Hadley before the authors were aware that Mr. E. H. Griffiths was engaged on a similar investigation. After a number of preliminary experiments, and just as the final arrangements for the conduct of the measurements were being definitely made, Mr. Hadley, on his appointment to the Head Mastership of the School of Science and Art, Kidderminster, had to leave Manchester. In the meantime Mr. Griffiths’ important research was published; and we had to consider whether our own work, which was designed on a smaller scale, could compete with it in accuracy. We decided to complete the investigation, principally for the reason that, although we both aimed at determining what is commonly called the mechanical equivalent of heat through the heating of a certain mass of water by means of an electric current, the details of the experiments differed very materially, so that our two ways of dealing with the problem seemed to afford a useful test of the amount of agreement which may be obtained at present. Our investigation touches only a small part of that treated by Mr. Griffiths, as we did not attempt to measure the changes in the specific heat of water due to change of temperature. On the other hand, the more modest limits within which we have confined ourselves, allowed us to use a much simpler apparatus. On Mr. Hadley’s departure, Mr. W. Gannon took his place. From the former gentleman we received a good deal of help in the devising and construction of some important parts of the apparatus. The principle of the method we have used is extremely simple. The electrical work done in a conductor being measured by ∫EC dt , where E is the difference of potential at the ends of the conductor, C the current and t the time, we keep the electromotive force constant, and measure ∫C dt directly by a silver voltameter. We do not therefore require to know the resistance of the wire, and we thus avoid the difficulty of having to estimate the excess of temperature of the wire over that of the water in which it is placed. We also gain the advantage of not having to measure time, and therefore are able to complete the experiment more quickly than we could have safely done if the length of time during which the current passed had to be measured with great accuracy.

Determination of aerobic work and power on a rope-braked cycle ergometer by direct measurement

2006 ◽  
Vol 31 (4) ◽  
pp. 392-397 ◽  
Author(s):  
Rae S. Gordon ◽  
Kathryn L. Franklin ◽  
Julien S. Baker ◽  
Bruce Davies
Keyword(s):  
Direct Measurement ◽  
Power Estimation ◽  
Cycle Ergometer ◽  
Mean Power ◽  
Physiological Assessment ◽  
Brake Force ◽  
The Mean ◽  
The Difference ◽  
Work Done

The purpose of this study was to compare the power and work outputs of a cycle ergometer using the manufacturer’s guidelines, with calculations using direct flywheel velocity and brake torque. A further aim was to compare the values obtained with those supplied by the manufacturer. A group of 10 male participants were asked to pedal a Monark 824E ergometer at a constant cadence of 60 r/min for a period of 3 min against a resistive mass of 3 kg. The flywheel velocity was measured using a tachometer. The brake force was determined by measuring the tension in the rope on either side of the flywheel. The calculated mean power was 147.45 ± 6.5 W compared with the Monark value of 183 ± 3.7 W. The difference between the methods for power estimation was 18% and was statistically significant (p < 0.01). The mean work done by the participants during the 3 min period was found to be 26 460 ± 1145 J compared with the Monark value of 33 067 ± 648 J (p < 0.01). The Monark formulae currently used to determine the power and work done by a participant overestimates the actual values required to overcome the resistance. There findings have far-reaching implications in the physiological assessment of athletic, sedentary, and diseased populations.

scholarly journals I. A determination of the specific heat of water in terms of the international electric units

1895 ◽  
Vol 57 (340-346) ◽  
pp. 24-32
Keyword(s):  
Specific Heat ◽  
Similar Investigation ◽  
Science And Art

This research was originally undertaken by Professor Schuster and Mr. H. Hadley, before the authors were aware that Mr. E. H. Griffiths was engaged on a similar investigation. After a number of pre­liminary experiments, and just as the final arrangements for the conduct of the measurements were being definitely made, Mr. Hadley, on his appointment to the Head Mastership of the School of Science and Art, Kidderminster, had to leave Manchester.

scholarly journals Experimental determination of the thermal conductivities of gases

1926 ◽  
Vol 110 (753) ◽  
pp. 91-122 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Experimental Determination ◽  
Dynamic Theory ◽  
Great Accuracy ◽  
Constant Volume ◽  
Order Of Accuracy ◽  
Molecular Collision ◽  
Thermal Conductivities

The analysis of the dynamic theory of gases has indicated an interesting relation between the viscosity η , the thermal conductivity K, and the specific heat at constant volume C c of a gas. This relation is represented by the expression K = f . C c . η , in which the factor f depends upon the law of force operative in molecular collision, and is known if K, C c , and η can be determined experimentally. In view of its importance in this respect, and also from the fact that great accuracy and consistency of measurement are possible in modern determinations of the viscosity of gases, the importance of the development of a method by which the conductivity can be measured with the same order of accuracy demands increasing attention.

THE MAINTENANCE OF A STANDARD OF ELECTROMOTIVE FORCE: NOTES ON STANDARD WESTON CELLS

1930 ◽  
Vol 3 (5) ◽  
pp. 473-489
Author(s):  
A. Norman Shaw ◽  
H. E. Reilley
Keyword(s):  
Electromotive Force ◽  
Essential Feature ◽  
Mean Deviation ◽  
Entire Group ◽  
Standard Cells ◽  
Characteristics Analysis ◽  
A Cell ◽  
The Mean ◽  
The Difference

A detailed procedure for the maintenance of a standard of voltage to within one or two parts in a million is described.In so far as these investigations have proceeded, neutral saturated cells have been found to be superior to acid cells as independent standards for a period of many years, though the latter are preferable for purposes of ordinary precision or shorter periods. The recommended code of procedure is briefly as follows: a number of cells should be constructed according to standard specifications with the new requirements of uniformity of container and speed of preparation, and observations made upon them every few days for a period of three months. The differences in electromotive force (at constant temperature) should be determined between each cell in the group and any one of them chosen arbitrarily as reference cell, and certain new selection and rejection rules applied. In accordance with these rules a cell should be rejected: (a) if its deviation from the mean electromotive force of the group has increased or decreased by 10 microvolts or more during the preceding two weeks; or (b) if it differs in electromotive force from the mean of the group by more than 10 +d microvolts where d is the mean deviation of the cells of the group. If d exceeds 20 microvolts the entire group should be considered untrustworthy. The selected cells should be observed for three additional months, the rejection rules again applied and if a specified proportion survive elimination, the initial reference mean of the laboratory may be established.At intervals of several months additional groups of cells, neutral and acid, should be constructed and exchanges made with laboratories possessing cells of known characteristics. Analysis of the resulting observations determines: (a) the constants in the aging* equation for the reference batch, and (b) the difference between the initial reference mean of the laboratory and the estimated value of the international reference mean.Examples of the analysis of cell observations are given, illustrating the establishment of the initial reference mean, the recapture of this value when the aging coefficients are known, and the preliminary determination of the aging equation for a given group of cells. The use of the aging equation is found to be the essential feature in the attainment of increased precision.A summary of data on standard cells is included.

I. Contact theory of voltaic action. Parts I and II

1878 ◽  
Vol 27 (185-189) ◽  
pp. 196-238 ◽  
Keyword(s):  
Electromotive Force ◽  
Zinc Sulphate ◽  
Copper Plate ◽  
Contact Theory ◽  
Metallic Contact ◽  
A Value ◽  
A Cell ◽  
The Difference ◽  
Voltaic Cell

The contact theory of voltaic action seems to have undergone no development since the date of Sir W. Thomson’s experiment, which consisted in connecting a plate of zinc and a plate of copper by means, of a drop of water, when it was found that the metals were brought to the same electric potential, although when metallically connected they were at different potentials. He believed that any electrolyte would behave in exactly the same way as the water of his experiment, equalizing the potentials of any two metals connected by it. The electromotive force of a simple cell, ought, in accordance with the theory, to be equal to the difference of potentials between zinc and copper in; contact. A test founded on this deduction was very difficult to apply, because there was no exact determination of the difference of potential of zinc and copper in contact, Sir W. Thomson, in his experiment, having really measured the difference of potential between air at the surface of a zinc plate, and air at the surface of a copper plate. In the absence of this test, the equality of the electromotive forces of simple cells in which zinc and copper are the metals (the liquids being water, dilute sulphuric acid, and sulphate of zinc) was held as a proof of the theory. Now it is known that when two pieces of the same metal are dipped into any two liquids, which are diffusing into one another, a difference of potentials is established between the metals, and the electromotive force of a cell of this kind can in no way depend on a difference of potentials due to metallic contact. So that although in such a cell there is an action which is somewhat the same as the action in a simple voltaic cell, the theory took no account of it whatever. In fact, the explanation of voltaic action given in the latest treatises on electricity is felt to be incomplete, even by the writers of such treatises, and the present investigation has been entered upon in consequence. Sir W. Thomson’s result, and our own experiments lead us to magine that when zinc and copper are immersed in water there are three successive states to be noticed:—At the instant of immersion the zinc and copper may be reduced to the same potential, so that the electromotive force of the voltaic cell E is equal to the difference of potential ZC — between zinc and copper in contact; the zinc now becomes negative to the copper, so that E reaches a limit which is greater than ZC — ; lastly, if a current passes, polarization occurs and the zinc becomes gradually less negative to the copper, E diminishing, therefore, from its maximum value# But when a saturated solution of zinc sulphate is employed instead of water, the first state, if it exists at all, exists for so short a time that practically, zinc and copper in zinc sulphate are never at the same potential. Thus (see Table X ) when care is taken to keep the zinc and copper in a water cell well insulated from one another, E is found to increase from a value very little greater than ZC — , the electromotive force of contact of zinc and copper, to a limit, but in a zinc sulphate cell no such great increase is observed.

II. Note on the atomic weight of glucinum or beryllium

1883 ◽  
Vol 35 (224-226) ◽  
pp. 248-250
Keyword(s):  
Specific Heat ◽  
Atomic Weight ◽  
Minute Quantity ◽  
The Difference ◽  
Atomic Heat

In the course of a paper by Professor Humpidge on the above subject, recently read before the Society, the author seeks to decide between the atomic weight 9·2 for beryllium, resulting from my comparison of the atomic heat of the element with that of silver and aluminium, and the value 13·8, arrived at by MM. Nilson and Pettersson by determination of specific heat.J The difference between the two possible atomic weights is so small, and the difficulties met with in attempting to prepare even a few decigrams of beryllium are so great, that both sets of experiments have been objected to on the ground, amongst others, that the metal employed was in all cases impure. My specimen admittedly contained a minute quantity of platinum, and the Proportion of known impurity in one of MM. Wilson and Pettersson's specimens reached 13 per cent. Unfortunately, Professor Humpidge's metal though claimed to be the purest yet prepared, is shown by analysis to be rather less pure than one of the specimens employed by Nilson and Pettersson, hence the experiments lately made known to the Society do not carry the inquiry beyond the point previously reached, save in one noteworthy particular, namely, that there appears to be a considerable, though irregular, rise in specific heat of the element as the proportion of impurity diminishes; but the value is still much below that required for the atomic weight 9·2. Thus for a specimen of beryllium which contained 13 per cent. of known of impurity Wilson and Pettersson obtained the specific heat 0·4084 between 0° and 100° C., and for a less impure specimen 0·425; while Professor Humpidge, in one of his experiments with a material that contained 6 per cent, of impurity, found the specific heat to be nearly 0·45 (0·4497). In all these cases corrections were applied which were believed to eliminate the effects due to the impurities known to be present—in part mechanically mixed with the metal and partly alloyed with it.

scholarly journals The heating effect of the currents in precise measurements of electrical resistance

1911 ◽  
Vol 85 (581) ◽  
pp. 541-556 ◽  
Keyword(s):  
Specific Heat ◽  
Applied Voltage ◽  
Electrical Resistance ◽  
Platinum Wire ◽  
Heating Effect ◽  
Mechanical Equivalent ◽  
Copper Manganese ◽  
The Wire ◽  
A Current

In a paper on the specific heat of water, one of us describes an experiment in which the passage of a current of 4·4 ampères through an oil-cooled manganin resistance of 1·2-mm. wire produced an increase in the resistance corresponding to an increase of temperature of 60° C. As the cooling surface of the resistance was 16 sq. cm. per watt, such a large increase of temperature was thought to be improbable, and the change of resistance was attributed to some other cause. However, the effect of the passage of the current was similar to that resulting on raising the temperature, and, because of this, it was proposed to call the change a thermoid effect. With platinum wires similar results were obtained, the increase of resistance being nearly proportional to the square of the current and inversely proportional to the radius of the wire. The change of resistance with varying current was investigated by Dr. E. H. Griffiths in 1893. Using a fine platinum wire, he found the increase of resistance to be proportional to the square of the applied voltage. With regard to this increase, Dr. Griffiths remarks:—“It seemed absolutely immaterial whether the current was on for only a few seconds or indefinitely.” Previous experiments on an alloy of copper, manganese, and nickel had shown that the resistance of the alloy changed appreciably in the course of one and a-half hours when a current of ½ ampère was passed through it, and Dr. Griffiths states that the rise appeared to be a function of the current rather than of the time. If, in Dr. Griffiths’ determination of the mechanical equivalent of heat, he had neglected the rise of resistance of the wire with increasing current, an error of about 1 part in 60 would have been introduced.

scholarly journals A NEW METHOD FOR MEASURING TOTAL POROSITY IN HORTICULTURAL SUBSTRATES

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1093c-1093
Author(s):  
William C. Fonteno
Keyword(s):  
Bulk Density ◽  
Particle Density ◽  
Total Porosity ◽  
Great Accuracy ◽  
Modified Method ◽  
New Apparatus ◽  
The Difference ◽  
Mineral Soils ◽  
Container Capacity

The determination of air and water holding capacities of horticultural substrates has been plagued by errors in measurement. The amount of air and water held at container capacity is influenced by the substrate and container height. Container capacity can be established through specific measurement. Air space, the difference between total porosity and container capacity, is usually poorly determined because of errors in total porosity measurement. Most researchers calculate total porosity (St) from the formula: St = 1-(ρb/ρp), where ρb is the dry bulk density and ρp is the particle density. While bulk density is usually measured, particle density is not. Many times an average ρp of 2.65 Mg·m-3 for mineral soils is used. This sometimes creates large errors in calculating total porosity because the values of ρp for horticultural substrates range from 0.35 to 2.1 Mg·m-3. Total porosity can be measured with great accuracy at 0 kPa tension on a pressure plate apparatus, but is costly in equipment and time. Using a modified method of extraction and a new apparatus, using standard aluminum soil sampling cylinders, total porosity was measured with an 85% reduction in time end no decrease in accuracy.

scholarly journals Determination of residual strain in steel wire cord by chemical method

2019 ◽  
pp. 72-75
Author(s):  
N. A. Zmeeva
Keyword(s):  
Residual Strain ◽  
Chemical Method ◽  
Steel Wire ◽  
Metal Wire ◽  
Residual Strains ◽  
The Wire ◽  
The Difference ◽  
Strength And Durability

The article presents a method for determining the residual strain in the steel wire cord of construction 3x0,30. The causes of residual strain, the effect on the quality of finished product and the determination of the degree of residual strain by chemical method are considered. The cause of residual strain is uneven plastic deformation of a solid body due to various changes in different places of its length and volume. Residual strain of steel wire cord are made up of stresses existing in the wire after drawing, and the stresses created during the lay of wire.An important task in the framework of the metal wire cord manufacturing technology, which is faced by specialists at «BMW» – the Management Company of the Holding «BMC» is to reduce residual strains at all stages of metal wire cord manufacturing. Residual strains are an additional factor affecting the adhesive strength and durability of adhesive joints.The principle of determining the residual strains is to remove the coating from the metal wire cord, paint the transverse halves of each thread. Then the filaments are impregnated with nitric acid, and the residual strain on the surface is recorded as the difference between the residual strains of the two halves of the wire.

scholarly journals VI. The value of the mechanical equivalent of heat, deduced from some experiments performed with the vieiv of establishing the relation between the electrical and mechanical units; together with an investigation into the capacity for heat of water at different temperatures

1893 ◽  
Vol 184 ◽  
pp. 361-504 ◽  
Keyword(s):  
Specific Heat ◽  
Electric Current ◽  
Fundamental Unit ◽  
Electrical Measurements ◽  
Mechanical Equivalent ◽  
Physical Measurements ◽  
Different Temperatures ◽  
The Absolute ◽  
Work Done

The necessity for a re-determination of the value of the mechanical equivalent may not be obvious at first sight. The classic determinations by Joule have undergone but little alteration at the hands of succeeding observers, and the researches of Rowland (1879) into this matter were of such an exhaustive nature that there would appear to be little room left for farther investigation. It should, however, remembered that even Joule’s later determinations differ by as much as1 part in 100*; and that marvellous as is the agreement, amongst themselves, of the results obtained by Rowland, they, since his method of investigation was unaltered throughout, stand in need of confirmation by different methods of observation. Again, Rowland, as far as I have been able to ascertain, stands practically alone in his conclusion that the specific heat of water diminishes as the temperature rises from 0° to 30° C. I t is difficult to conceive of a more important investigation (for the purposes of accurate physical measurements) than the determination of the capacity for heat of water at different temperatures, and it is to me a matter of extreme surprise that greater efforts have not been made to trace the variation (if any) in its value. The science of calorimetry must be regarded as in its infancy so long as its fundamental unit is a matter of doubt. Other observers who have attempted to obtain the value of the mechanical equivalent, by means of the work done by an electric current, have been hampered by constant perplexities as to the absolute values of the electrical units adopted. The science of electrical measurements has now arrived at such a stage that its units may be regarded as sufficiently established,t and, therefore, the time seems parti­cularly appropriate for an enquiry into the relation between those units and the mechanical ones.

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