5. On the Currents produced by Contact of Wires of the same Metal at different Temperatures

1872 ◽  
Vol 7 ◽  
pp. 788-791
Author(s):  
W. Durham
Keyword(s):  
Electric Current ◽  
High Temperatures ◽  
The Other ◽  
Thermo Electric ◽  
Different Temperatures ◽  
The One

At the suggestion of Professor Tait, I undertook the investigation of the momentary thermo-electric current developed when two conductors or wires of the same metal are brought into contact, the one being at a different temperature from the other.Platinum was chosen as the most suitable metal to experiment with, in the first instance, as it is free from the interfering action of oxidation at high temperatures.

scholarly journals An enquiry concerning the nature of heat, and the mode of its communication

1832 ◽  
Vol 1 ◽  
pp. 139-147
Keyword(s):  
Principal Part ◽  
Cylindrical Vessel ◽  
The Other ◽  
Metallic Surface ◽  
Previous Trial ◽  
Flat Surfaces ◽  
Different Temperatures ◽  
The One ◽  
Quantity Of Heat

The importance of the investigation here entered into,—inasmuch as it applies to most of the operations of nature as well as art,—appears so manifest, that we shall not recapitulate what the author advances on that subject. Before he proceeds to the detail of his experiments for the purpose of computing the emissions of heat from various bodies under a variety of circumstances, he finds it necessary to premise a minute description of the principal part of the apparatus he contrived for his purpose. This instrument consists of a hollow cylindrical vessel of brass, four inches long, and as many in diameter. It is closed at both ends; but has at one end a cylindrical neck about eight-tenths of an inch in diameter, by which it is occasionally filled with water of different temperatures, and through which also a thermometer, constructed for the purpose, is occasionally introduced, in order to ascertain the changes of temperature in the fluid. As it was in the first instance only meant to observe the quantity of heat that escapes through the sides of the vessel, two boxes were contrived, filled and covered with non-conducting substances, such as eiderdown, fur, &c., which were fitted to the two ends or flat surfaces of the cylinder. Six of these instruments, with proper stands, and auxiliary implements of obvious construction, were prepared for the sake of comparative experiments. A previous trial was made with two of the cylinders, the vertical polished sides of the one being naked, and those of the other covered with one thickness of fine white Irish linen, strained over the metallic surface. Here it was found, contrary to expectation, that in a certain space of time the covered cylinder had lost considerably more heat than the naked one.

scholarly journals On the magnetic power of soft iron

1837 ◽  
Vol 3 ◽  
pp. 187-188
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
Complete Removal ◽  
The Other ◽  
Present Communication ◽  
Hard Steel ◽  
Electric Current Passing ◽  
Good Contact ◽  
The One ◽  
Single Helix

When free magnetism is developed by induction, and is not retained in that state by what has been termed the coercive force of hard steel, it has generally been considered that all the phenomena due to the existence of free magnetism cease on the removal of the inducing cause. The object of the present communication is to show that such is not the fact. From a variety of experiments described by the author, it appears that soft iron continued to exhibit strongly the attraction due to the developement of magnetism long after the means by which the magnetism had been originally excited had ceased to act. In these experiments, bars of soft iron, in the form of a horseshoe, had a single helix of copper wire wound round them, so that on the ends of the wire being brought into contact with the poles of a voltaic battery, the iron became an electromagnet. With one of these horse-shoes, while the connexion between the ends of the helix and the poles of the battery existed, the soft iron, having a keeper applied to its poles, supported 125 pounds it supported 56 pounds after that connexion had been broken, and continued to retain the power of supporting the same weight after an interval of several days, care having been taken not to disturb, during the time, the contact between the horse-shoe and its keeper. On this contact, however, being broken, nearly the whole attractive power appeared to be immediately lost. The author describes several instances of the same kind, particularly one in which the contact between the ends of the horse-shoe of soft iron and its keeper having been undisturbed during fifteen weeks, the attractive power continued undiminished. Although the interposition of a substance, such as mica or paper, between the ends of the horse-shoe and its keeper necessarily diminished the force of attraction, it did not appear to diminish the power of retaining that force. In a case where the electromagnet of soft iron and its keeper were equal semi-circles, the author found, what may appear singular, that the arrangement of the magnetism during the time that the electric current traversed the helix, appeared not to be the same as after the cessation of that current; in the one case similar, and in the other dissimilar, poles being opposed to each other at the opposite extremities of the two semi-circles. Whether the magnetism was originally developed in the soft iron by means of an electric current passing round it, or by passing over its surface the poles of an electromagnet, or those of a common magnet of hard steel, it appeared to possess the same power of retaining a large portion of the magnetism thus developed. The retention of the magnetism does not appear to depend upon the relative positions of the ends of the horse-shoe and the keeper remaining undisturbed, but on their contact remaining unbroken: for one keeper was substituted for another without diminution of this power; care being taken that the second should be in good contact with both ends of the horse-shoe before the complete removal of the first.

scholarly journals On a new register-pyrometer, for measuring the expansions of solids, and determining the higher degrees of temperature upon the common thermometric scale

1833 ◽  
Vol 2 ◽  
pp. 404-406
Keyword(s):  
Melting Point ◽  
High Temperatures ◽  
The Other ◽  
Royal Institution ◽  
Guyton De Morveau ◽  
Higher Temperature ◽  
The Subject ◽  
The Common ◽  
The One ◽  
Universal Application

In the year 1821, the author published in the Journal of the Royal Institution an account of a new pyrometer, and of some determinations of high temperatures, in connexion with the scale of the mercurial thermometer, obtained by its means. The use of the instrument then described was, however, limited; and the author was subsequently led to the invention of a pyrometer of a more universal application, both to scientific researches and to various purposes of art. Fie introduces the subject by an account of the late attempt of M. Guyton de Morveau, to employ the expansions of platina for the admeasurement of high temperatures, and for connecting the indications of Wedgwood’s pyrometer with the mercurial scale, and verifying its regularity. The experiments of that philosopher were by the contraction of porcelain, and by actual comparison with those of the platina pyrometer, at no higher temperature than the melting point of antimony; but they are sufficient to establish the existence of a great error in Wedgwood’s original estimation of his degrees up to that point. This he carries on by calculation, on the hypothesis of uniform progression of expansion, up to the melting point of iron; the construction of his instrument not admitting of its application to higher temperatures than a red heat, in which platina becomes soft and ductile. Mr. Daniell shows, by an examination of M. Guyton’s results, that he has failed in establishing the point he laboured to prove; namely, the regularity of the contraction of the clay pieces. The pyrometer of the author consists of two distinct parts; the one designated the register , the other the scale .

scholarly journals The influence of homodromous and heterodromous electric currents on transmission of excitation in plant and animal

1915 ◽  
Vol 88 (607) ◽  
pp. 483-507 ◽  
Keyword(s):  
Electric Current ◽  
The Other ◽  
Muscle Preparation ◽  
Mimosa Pudica ◽  
Electric Currents ◽  
Joint Effects ◽  
Conducting Tissue ◽  
The One ◽  
Conduction Of Excitation ◽  
Stimulation Of

I have in a previous paper described investigation on the conduction of excitation in Mimosa pudica . It was there shown that the various characteristics of the propagation of excitation in the conducting tissue of the plant are in every way similar to those in the animal nerve. Hence it appeared probable that any newly found phenomenon in the one case was likely to lead to the discovery of a similar phenomenon in the other. A problem of great interest which has attracted my attention my attention for several years is the question whether, in a conducting tissue, excitation travels better with or against the direction of an electric current. The experimental difficulties presented in the prosecution of this enquiry are very numerous, the results being complicated by the joint effects of the direction of current on conductivity and of the poles on excitability. As regards the latter, the changes of excitability in the animal nerve under electrotonus have been demonstrated by the well-known experiments of pflüger. In a nerve-and-muscle preparation, the presence of a pole P is shown to induce a variation of excitability of a neighbouring point S. When P is kathode, the excitability of the point S, near it, is enhanced; stimulation of S, previously ineffective, now becomes effective, and the resulting excitation is transmitted to M, causing response of the muscle. Conversely, the application of anode at P causes a depression of excitability of S. Stimulus previously effective now becomes ineffective. In this manner the transmission of excitation may be indirectly modified by the polar variation of excitability of the stimulated point (fig. 1 a ).

scholarly journals The method of meningostomy and its application in the study of the brain in animals

2021 ◽  
Vol 27 (8) ◽  
pp. 820-821
Author(s):  
A. I. Smirnov ◽  
P. D. Olefirenko
Keyword(s):  
Cerebral Cortex ◽  
Electric Current ◽  
Brain Stimulation ◽  
Thermal Effects ◽  
Brain Injuries ◽  
The Other ◽  
Surgical Methods ◽  
The One ◽  
The Brain ◽  
Gain Access

All surgical methods used in the study of the brain in animals can be combined into two groups: 1) methods of direct and indirect shutdown of a particular part of the brain and 2) methods of non-mediocre brain stimulation by electric current or by mechanical, chemical or thermal effects. In the hands of different experimenters, depending on the goals and objects of research, these basic methods varied to one degree or another. All modifications were aimed at, on the one hand, to avoid brain injuries during trepanation as much as possible, and on the other hand, to gain access to the cerebral cortex without exposing it at the time of the observation itself. As can be judged from the literature collected from E. Abderhalden in Handbuch der biolog. Arbeitsmethoden to a certain extent this has already been achieved.

scholarly journals XIX. On the thermo-electric series

1858 ◽  
Vol 148 ◽  
pp. 369-381 ◽  
Keyword(s):  
The Other ◽  
Electric Currents ◽  
Philosophical Magazine ◽  
Thermo Electric ◽  
Different Temperatures ◽  
Alkaline Earths ◽  
Two Temperatures ◽  
The Difference

Being enabled by the method described in the Philosophical Magazine (February 1857) to obtain wires of the metals of the alkalies and alkaline earths, I have determined their places, together with most of those of the other metals and some alloys, in the thermo-electric series. The alloys which were experimented with, are those described by Rollman as giving with other metals stronger thermo-electric currents than those of bismuth or antimony under the same circumstances. If A, B, C are different metals, and (A, B), (B, C), (C, A) the electromotive powers of thermo-elements formed out of each two of these metals, whose alternate soldering-points are at two different temperatures, then (A, B)+(B, C)+(C, A) = 0, and therefore (A, B) = a-b , (B, C) = b-c , (C, A) = c-a , where the values of a, b, c not only depend on the two temperatures, but also on the nature of each of the metals A, B, and C. As the "differences” of the same constitute the electromotive powers, the value for any one of these metals may be put = 0. If the temperatures of the soldering-points of a thermo-element only vary slightly, the electromotive power may be said to be proportional to the difference of the two temperatures, and under the same conditions the quantities a, b, c are also proportional to the difference of the temperatures, and their ratios to each other therefore independent of the same. If now the value of a second metal relative to the above-named value of the first be taken = 1, the values of the others in relation to these can be deduced, and only depend on the nature of each metal. These values I will call the Thermo-electric Numbers of the metals.

XVIII. On an instrument for correcting gaseous volume

1883 ◽  
Vol 34 (220-223) ◽  
pp. 166-167 ◽  
Keyword(s):  
The Other ◽  
Small Glass ◽  
Different Temperatures ◽  
Glass Tubes ◽  
Temperature And Pressure ◽  
The One ◽  
Square Box ◽  
Small Cylinder

This instrument has been devised in order to facilitate the correction of the observed volume of a mass of gas, measured at any common temperature and pressure, to the volume the gas would occupy if measured under standard conditions. A reading of the instrument furnishes a number which serves for the making of this correction, and stands instead of readings of the barometer and of the thermometer, and a reference to a table of the tension of aqueous vapour at different temperatures. The instrument consists of two small glass tubes standing side by side; the one is open above, having been drawn out and bent down-wards to exclude dust; the other tube terminates in a bulb whose Capacity is about four and a half times that of the tube. The two tubes are connected below by means of caoutchouc tubing with a small cylinder containing mercury, closed above by a leather cap, which can be pressed down by a button attached to a screw moving m a fixed socket W hen the screw and button are lowered the mercury rises in both tubes. The ends of the tubes and the reservoir of mercury are contained in a square box, upon the bottom of which they rest and whose top carries the socket in which the screw turns. At the back of the box is a wooden upright which supports the tubes The tube which terminates in a bulb is graduated and figured so as to m ark the capacity of the bulb and tube, down to each line of graduation.

scholarly journals VI. Thermo-electric properties of salt solutions

1894 ◽  
Vol 55 (331-335) ◽  
pp. 356-373
Keyword(s):  
Electrical Properties ◽  
Electromotive Force ◽  
Electric Properties ◽  
The Other ◽  
Salt Solutions ◽  
Metallic Wire ◽  
Thermo Electric ◽  
Different Temperatures ◽  
The Difference

The thermo-electrical properties of solutions have not hitherto received much attention from physicists. If we form a circuit of two substances, one a metallic wire and the other a solution, and arrange it so that the junctions between the metal and the liquid are at different temperatures, we generally find that an electromotive force is developed in the circuit which varies in magnitude nearly in proportion to the difference of temperature between the junctions, and which, in comparison with the ordinary thermo-electromotive forces in metallic circuits, is very considerable. Up to the present time, as far as I am aware, the only extensive measurements of such thermo-electric forces are those of M. Bouty (‘Journ. de Phys., vol. 9).

scholarly journals Microwave Treatments of Cereals: Effects on Thermophysical and Parenchymal-Related Properties

Foods ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 711
Author(s):  
Anna Angela Barba ◽  
Carlo Naddeo ◽  
Silvestro Caputo ◽  
Gaetano Lamberti ◽  
Matteo d’Amore ◽  
...  
Keyword(s):  
Physical Properties ◽  
Heat Transport ◽  
Structural Properties ◽  
High Temperatures ◽  
The Other ◽  
Texture Change ◽  
Germination Ability ◽  
Heat Transport Properties ◽  
Mineral Losses ◽  
The One

Dielectric heating is one of the most interesting techniques for pest disinfestation. However, most of the literature works give information about the ability of microwave treatments at different power-time conditions to kill insects; less is given about the analysis of matrices structural properties and heat transport. Accordingly, the aim of this work is to investigate the effect of microwave treatments, applied for pest disinfestation, on heat transport behavior and physical/structural properties, such as water uptake capability, mineral losses, texture change, and germination capability, of most consumed cereals in human diet, such as weak wheat, durum wheat, and corn. Two different radiative treatments were performed: one in time-temperature conditions capable of inactivating the weed fauna, and the other at high temperatures of ~150 °C, simulating uncontrolled treatments. Heat transport properties were measured and showed to keep unvaried during both effective and uncontrolled microwave treatments. Instead, grain physical properties were worsened when exposed to high temperatures (reduction of germination ability and texture degradation). The achieved results, on the one hand, provide new structural and heat transport data of cereals after microwave treatments, actually not present in the literature, and on the other, they confirm the importance of correctly performing microwave treatments for an effective disinfestation without affecting matrices physical properties and nutritional features.

scholarly journals XIV. Experimental researches in electricity.—Tenth series

1835 ◽  
Vol 125 ◽  
pp. 263-274
Keyword(s):  
Electric Current ◽  
Royal Society ◽  
The Other ◽  
The One ◽  
Experimental Researches

1119. I have lately had occasion to examine the voltaic trough practically, with a view to improvements in its construction and use; and though I do not pretend that the results have anything like the importance which attaches to the discovery of a new law or principle, I still think they are valuable, and may therefore, if briefly told, and in connexion with former papers, be worthy the approbation of the Royal Society. 16. On an improved form of the Voltaic Battery . 1120. In a simple voltaic circuit (and the same is true of the battery) the chemical forces which, during their activity, give power to the instrument, are generally divided into two portions; the one of these is exerted locally, whilst the other is transferred round the circle (947. 996.); the latter constitutes the electric current of the instru­ment, whilst the former is altogether lost or wasted. The ratio of these two portions of power may be varied to a great extent by the influence of circumstances: thus, in a battery not closed, all the action is local; in one of the ordinary construction, much is in circulation when the extremities are in communication; and in the perfect one, which I have described (1001.), all the chemical power circulates and becomes elec­tricity. By referring to the quantity of zinc dissolved from the plates (865. 1126.), and the quantity of decomposition effected in the volta-electrometer (711. 1126.) or elsewhere, the proportions of the local and transferred actions under any particular circumstances can be ascertained, and the efficacy of the voltaic arrangement, or the waste of chemical power at its zinc plates, be accurately determined.

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