scholarly journals VII. Experimental researches in electricity.-Twenty-third Series

1850 ◽  
Vol 140 ◽  
pp. 171-188 ◽  
Keyword(s):  
Magnetic Field ◽  
Mode Of Action ◽  
Royal Society ◽  
The Other ◽  
Experimental Proof ◽  
Philosophical Paper ◽  
Iron Nickel ◽  
The One ◽  
Experimental Researches ◽  
The Magnetic Field

Four years ago I suggested that all the phenomena presented by diamagnetic bodies, when subjected to the forces in the magnetic field, might be accounted for by assuming that they then possessed a polarity the same in kind as, but the reverse in direction of, that acquired by iron, nickel and ordinary magnetic bodies under the same circumstances (2429. 2430.). This view was received so favourably by Plücker, Reich and others, and above all by W. Weber, that I had great hopes it would be confirmed; and though certain experiments of my own (2497.) did not increase that hope, still my desire and expectation were in that direction. Whether bismuth, copper, phosphorus, &c., when in the magnetic field, are polar or not, is however an exceedingly important question; and very essential and great differences, in the mode of action of these bodies under the one view or the other, must be conceived to exist. I found that in every endeavour to proceed by induction of experiment from that which is known in this department of science to the unknown, so much uncertainty, hesitation and discomfort arose from the unsettled state of my mind on this point, that I determined, if possible, to arrive at some experimental proof either one way or the other. This was the more needful, because of the conclusion in the affirmative to which Weber had come in his very philosophical paper; and so important do I think it for the progress of science, that, in those imperfectly developed regions of knowledge, which form its boundaries, our conclusions and deductions should not go far beyond, or at all events not aside from the results of experiment (except as suppositions), that I do not hesitate to lay my present labours, though they arrive at a negative result, before the Royal Society.

scholarly journals The Role of Magnetic Field for Quiescence-Outburst Models in CVs

2015 ◽  
Vol 2 (1) ◽  
pp. 192-196
Author(s):  
S. De Bianchi ◽  
V. F. Braga ◽  
S. Gaudenzi
Keyword(s):  
Magnetic Field ◽  
Complex Systems ◽  
Cataclysmic Variables ◽  
The Other ◽  
Suitable Candidate ◽  
Global Behaviour ◽  
The One ◽  
Thermonuclear Runaway ◽  
The Magnetic Field

In this paper we present the elementary assumptions of our research on the role of the magnetic field in modelling the quiescence-outbursts cycle in Cataclysmic Variables (CVs). The behaviour of the magnetic field is crucial not only to integrate the disk instability model (Osaki 1974), but also to determine the cause and effect nexus among parameters affecting the behavior of complex systems. On the ground of our interpretation of the results emerging from the literature, we suggest that in models describing DNe outbursts, such as the disk instability model, the secondary instability model (Bath 1973) and the thermonuclear runaway model (Mitrofanov 1978), the role of the magnetic field is at least twofold. On the one hand, it activates a specific dynamic pathway for the accreting matter by channelling it. On the other hand, it could be indirectly responsible for switching a particular outburst modality. In order to represent these two roles of the magnetic field, we need to integrate the disk instability model by looking at the global behaviour of the system under analysis. Stochastic resonance in dynamo models, we believe, is a suitable candidate for accomplishing this task. We shall present the MHD model including this mechanism elsewhere.

Experimental and Theoretical Investigation of the Giant MR-Effect

2014 ◽  
Author(s):  
Christian Hegger ◽  
Jürgen Maas
Keyword(s):  
Magnetic Field ◽  
Experimental Investigation ◽  
Yield Stress ◽  
Normal Force ◽  
The Other ◽  
Modeling Approach ◽  
Good Accordance ◽  
The One ◽  
Mr Effect ◽  
The Magnetic Field

This contribution deals with the theoretical and experimental investigation of the giant MR-effect. The giant MR-effect can be utilized to increase the yield stress of magnetorheological fluids (MRF). To obtain a boost of the yield stress the MRF has to be normally compressed while it is exposed to a magnetic field in order to create stronger particle structures. For the experimental investigation a MRF test actuator with an conical shear gap is designed, enabling an adjustment of the shear gap’s height by applying a compressing normal force. The experimental investigation points out that a potentially increase of the yield stress can be achieved on the one hand. On the other hand it is dependent on the magnetic field strength during the compression as well as on the shear rate and shear strain. The results are used to motivate a modeling approach which combines the rheological behavior with tribological effects. The validation of the modeling approach shows a good accordance to the behavior of the physical investigated giant MR-effect.

scholarly journals The Complex Behaviour of High-Frequency Currents in Simple Circuits

1947 ◽  
Vol 40 (12) ◽  
pp. 741-748
Author(s):  
P. Bauwens
Keyword(s):  
Magnetic Field ◽  
Transmission Lines ◽  
High Frequency ◽  
Eddy Currents ◽  
Electrical Energy ◽  
The Body ◽  
The Other ◽  
Complex Behaviour ◽  
The One ◽  
The Magnetic Field

The fact that standing wave phenomena exist along transmission lines and loops conducting high-frequency electrical energy is responsible for effects of which therapeutic use can be made. A. Power measurements are made possible because parallel transmission lines behave as power transformers of which the ratio varies with the length of these lines. In a generator designed by the G.E.C. the dimensions of the lines are such that after a preliminary estimation of the impedance of the load in the treatment field, the sensitivity of the meter can be adjusted so that the meter subsequently registers in watts the power absorbed in this load. B. When using cable electrodes, in practice, the presence of strong electric fields between the antinodal portions of the loop as well as strong oscillating magnetic fields around the nodal portion gives rise to two distinct phenomena (fig. 6). Search for currents resulting from the electric field on the one hand, and for eddy currents due to the magnetic field on the other, was carried out at St. Thomas's Hospital, in liquid phantoms by means of a probe (fig. 5 a) incorporating a small lamp capable of being rotated in every direction. Voltage measurements were recorded by matching its light intensity with that of a similar lamp in circuit with a variable resistance and a voltmeter (fig. 5 b). When a portion of a cable electrode was coiled around a cylindrical vessel containing an electrolyte, the effects due to the two conditions could be dissociated. The following observations were made (fig. 7): ( a) By using the nodal portions of the loop only, it was shown that only eddy currents are produced and that the lower the resistance of the electrolyte the more easily they are produced. They are strongest at the periphery and rapidly fall off away from it, as shown by the curves of the graph in fig. 8. ( b) By using only the antinodal portions of the loop, coiled around the same vessel, coaxial or longitudinal currents can be demonstrated. It is interesting to note that these exist both at the periphery and at the centre. ( c) When the whole cable is wound around the vessel, the concentration of the electrolyte becomes the factor determining the way in which the energy will be dissipated: (1) with tap-water, it is found that no eddy currents can be demonstrated whereas coaxial currents exist; (2) with strong saline solutions the converse holds good; (3) with electrolytes of intermediate concentration both types of currents can be shown to coexist at the periphery while at the centre only coaxial currents can be demonstrated. The fact that eddy currents and coaxial currents could be detected simultaneously and did not, as might be expected, give rise to a resultant, could only be explained by assuming that although eddy currents and coaxial currents coexisted as far as their effects on the pilot lamp were concerned, these two phenomena were not coincident as regards their phase relations. On examining the system more closely it became clear that the coaxial currents must be approximately 90 degrees out of phase with the eddy currents. By means of another type of probe (fig. 5 c) for surface work, consisting of two metallic buttons mounted on an insulating strip and bridged by a small lamp, P3, similar to the one used throughout the investigations, it was possible to show that the same conditions existed in the body. It could be demonstrated that both coaxial and eddy currents occurred and that the predominance of one or the other type was dictated by conditions related to impedance. In the thigh just above the knee-joint, in most cases both currents could be demonstrated. It could also be shown that when half the cable was wound clockwise and the other half anticlockwise, so as to cancel the magnetic field between the two halves, no eddy currents existed. C. Present therapeutic applications of high-frequency currents involve the continuous dissipation of electrical energy in the load under treatment. Under these conditions the only detectable effect to which therapeutic value may be ascribed is the rise in temperature which results from heat production. This rise in temperature sets a limit to the power which can be used without risk of burns. Consequently effects other than thermal ones which might manifest themselves under higher intensities remain undetected. It is not possible to predict what would happen if, instead of treating tissues by means of sustained high-frequency electrical energy, tissues were subjected to intermittent radio-frequency pulses of very high intensity separated by silent periods of sufficient length to allow for the dissipation of heat. Those who have some technical knowledge of such matters will readily recognize an application of “Radar” technique in this.

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.

The magnetic field Influence on the absorption threshold of VOâ‚‚

2016 ◽  
pp. 3322-3332
Author(s):  
Abderrahim Ben Chaib
Keyword(s):  
Magnetic Field ◽  
Vanadium Dioxide ◽  
Abrupt Change ◽  
The Other ◽  
Electron Hole ◽  
Quasi Particle ◽  
Metal State ◽  
The One ◽  
The Magnetic Field ◽  
Field Influence

The vanadium dioxide VO₂ is a material described as being intelligent because it can transit [1,2] from a reversible way of the semiconductor state to the metal state at a temperature θt = 68°C. When we are at a temperature θt < 68°C, this material is in the semiconductor state with a gap [3,4] approximately 0.7 ev. When θt > 68°C, the vanadium dioxide becomes metal [14], there is an abrupt change of its structure and its optical properties [14,15] and electronic. We are interested in this study in the VO₂ semiconductor state [15] and, especially, in widening its gap by the application of a magnetic field B = Bz . By taking into account the spin of the electron of the band of conduction after having neglected the term of Coulomb interaction, we solved the Schrödinger’s equation in an exact way. Obtaining the levels of Landau [5,6,7] enables us to conclude the variation of the gap of ΔEg = 1 2 ℏωc, where ωc is the frequency cyclotron ωc = eB μ, with e: theelectron charge; μ: the reduced mass of the quasi particle (electron-hole); ħ: the Planck's constant reduced, and B is the intensity of the applied magnetic field. We will simulate by Maple this variation according to B for fixed μ on the one hand, and ΔEg according to μ for fixed B on the other hand.

scholarly journals IX. Experimental researches in electricity.—Thirtieth series

1856 ◽  
Vol 146 ◽  
pp. 159-180 ◽  
Keyword(s):  
Magnetic Field ◽  
Royal Society ◽  
Surrounding Medium ◽  
Electric Currents ◽  
Magnetic Action ◽  
Different Temperatures ◽  
The One ◽  
New Phenomena ◽  
Experimental Researches ◽  
Lines Of Force

3363. Whilst using lines of force as a true, searching, and as yet, never-failing representative of the one form of power possessed by paramagnets, diamagnets, and electric currents,—and whilst endeavouring simultaneously to make the principle of representation a key to new phenomena, and subjecting the principle itself to rigid cross examination,—I have had occasion to examine the action of certain magnetic bodies in different media and at different temperatures; and as the results are true, and must, therefore, be valuable in any view of the cause of magnetic action, I have thought them worthy of presentation to the Royal Society. 3364. When an unmagnetized but magnetic body, placed in a magnetic field, is affected by the forces thrown upon it, and under their action sets , or takes up a definite position, the effect may depend upon its peculiar molecular condition, or upon its relation to the surrounding medium, or upon both conjointly, or upon one or both combined with temperature. Some of each of these conditions have been the objects of my investigations.

scholarly journals Experimental researches in electricity. Twenty-sixth series. On magnetic conducting power and atmospheric magnetism

1851 ◽  
Vol 5 ◽  
pp. 998-1000
Keyword(s):  
Magnetic Field ◽  
Differential Effect ◽  
Magnetic Force ◽  
The Other ◽  
Parallel Lines ◽  
Magnetic Action ◽  
Magnetic Poles ◽  
Experimental Researches ◽  
The Magnetic Field ◽  
Two Bodies

The remarkable results respecting oxygen and nitrogen described in the last Series, and the absence of any change of volume under strong magnetic action, led the author to apply for a time the idea of conducting power to the magnetic phenomena there described, meaning by that phrase the capability which bodies possess of affecting the transmission of the magnetic force without any reference to the process by which that transmission is effected; and assuming that two bodies are at the same time in the magnetic field, and that one displaces the other, he considers the result as a differential effect of their difference in conducting power. If a free portion of space be considered with lines of equal magnetic force passing across it, they will be straight and parallel lines. If a sphere of paramagnetic matter be placed in such a space, they will gather upon and in the sphere, being no longer parallel in their course, nor of equal intensity in every part; or if a sphere of diamagnetic matter replace the former sphere, the lines of force will open out where the sphere is, being again no longer parallel in direction nor uniform in force. When the field of magnetic force is formed between the opposite flat ends of two large magnetic poles, then these are affected, and the globes also, and there are mutual actions; a paramagnetic body, if a little elongated, points axially and tends to go to the iron walls of the field, whilst a similar diamagnetic body points equatorially, and tends to go to the middle of the field. Paramagnetic bodies repel each other, and so also do diamagnetic bodies; but one of each class being taken, they attract one another.

scholarly journals Description of a new barometer, recently fixed up in the apart­ments of the Royal Society; with remarks on the mode hitherto pursued at various periods, and an account of that which is now adopted, for correcting the observed height of the mercury in the society’s barometer

1843 ◽  
Vol 4 ◽  
pp. 1-3
Keyword(s):  
Royal Society ◽  
The Other ◽  
Chemical Effect ◽  
The Absolute ◽  
The One ◽  
And Control ◽  
Usual Scale

The barometer, here alluded to, may in some measure be consi­dered as two separate and independent barometers, inasmuch as it is formed of two distinct tubes dipping into one and the same cistern of mercury. One of these tubes is made of flint glass, and the other of crown glass, with a view to ascertain whether, at the end of any given period, the one may have had any greater chemical effect on the mercury than the other, and thus affected the results. A brass rod, to which the scale is attached, passes through the framework, between the two tubes, and is thus common to both : one end of which is furnished with a fine agate point, which, by means of a rack and pinion moving the whole rod, may be brought just to touch the surface of the mercury in the cistern, the slightest contact with which is immediately discernible; and the other end of which bears the usual scale of inches, tenths, &c.; and there is a separate vernier for each tube. A small thermometer, the bulb of which dips into the mercury in the cistern, is inserted at the bottom : and an eye­piece is also there fixed, so that the agate point can be viewed with more distinctness and accuracy. The whole instrument is made to turn round in azimuth, in order to verify the perpendicularity of the tubes and the scale. It is evident that there are many advantages attending this mode of construction, which are not to be found in the barometers as usu­ally formed for general use in this country. The absolute heights are more correctly and more satisfactorily determined ; and the per­manency of true action is more effectually noticed and secured. For, every part is under the inspection and control of the observer; and any derangement or imperfection in either of the tubes is imme­diately detected on comparison with the other. And, considering the care that has been taken in filling the tubes, and setting off the scale, it may justly be considered as a standard barometer . The pre­sent volume of the Philosophical Transactions will contain the first register of the observations that have been made with this instru­ment.

scholarly journals THE ENERGY EIGENVALUES OF THE TWO DIMENSIONAL HYDROGEN ATOM IN A MAGNETIC FIELD

2006 ◽  
Vol 15 (06) ◽  
pp. 1263-1271 ◽  
Author(s):  
A. SOYLU ◽  
O. BAYRAK ◽  
I. BOZTOSUN
Keyword(s):  
Magnetic Field ◽  
Hydrogen Atom ◽  
Iteration Method ◽  
Weak Magnetic Field ◽  
The Other ◽  
Asymptotic Iteration Method ◽  
Iterative Approach ◽  
Two Dimensional ◽  
Energy Eigenvalues ◽  
The Magnetic Field

In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the case with no magnetic field analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for n=2-10 and m=0-1 states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.

scholarly journals The influence of resistivity gradients on shock conditions for a Petschek reconnection geometry

2016 ◽  
Vol 34 (4) ◽  
pp. 421-425
Author(s):  
Christian Nabert ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Magnetic Field ◽  
Necessary Conditions ◽  
The Other ◽  
Diffusion Region ◽  
Two Dimensional ◽  
Characteristic Velocity ◽  
Magnetohydrodynamic Equations ◽  
One Dimensional ◽  
The Magnetic Field ◽  
Alfven Velocity

Abstract. Shock waves can strongly influence magnetic reconnection as seen by the slow shocks attached to the diffusion region in Petschek reconnection. We derive necessary conditions for such shocks in a nonuniform resistive magnetohydrodynamic plasma and discuss them with respect to the slow shocks in Petschek reconnection. Expressions for the spatial variation of the velocity and the magnetic field are derived by rearranging terms of the resistive magnetohydrodynamic equations without solving them. These expressions contain removable singularities if the flow velocity of the plasma equals a certain characteristic velocity depending on the other flow quantities. Such a singularity can be related to the strong spatial variations across a shock. In contrast to the analysis of Rankine–Hugoniot relations, the investigation of these singularities allows us to take the finite resistivity into account. Starting from considering perpendicular shocks in a simplified one-dimensional geometry to introduce the approach, shock conditions for a more general two-dimensional situation are derived. Then the latter relations are limited to an incompressible plasma to consider the subcritical slow shocks of Petschek reconnection. A gradient of the resistivity significantly modifies the characteristic velocity of wave propagation. The corresponding relations show that a gradient of the resistivity can lower the characteristic Alfvén velocity to an effective Alfvén velocity. This can strongly impact the conditions for shocks in a Petschek reconnection geometry.

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