W.-E. AYRTON et JOHN PERRY. — A new determination of the ratio of the electro-magnetic to the electrostatic unit of electric quantity (Nouvelle détermination du rapport de l'unité électromagnétique à l'unité électrostatique des quantités d'électricité) ; Phil. Magazine, 5e série, t. VII, p. 277; 1879

1879 ◽  
Vol 8 (1) ◽  
pp. 317-318
Author(s):  
G. Lippmann
Keyword(s):  
Electro Magnetic ◽  
Electric Quantity ◽  
John Perry

scholarly journals XII. A new current weigher and a determination of the electromotive force of the normal Weston cadmium cell

1908 ◽  
Vol 207 (413-426) ◽  
pp. 463-544 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic System ◽  
Electric Circuit ◽  
Secular Variations ◽  
System Of Units ◽  
Electro Magnetic ◽  
The Magnetic Field ◽  
A Current ◽  
Mutual Action

A Current can be measured absolutely in the electro-magnetic system of units either by means of the action of the current on a magnet, or of the current on a current. The former method has the disadvantage that at least two independent measurements are necessary. For example, in using an electro-magnetic balance, the strength of the magnet acted on by the electric circuit has to be determined, as well as the force exerted on the magnet by the circuit. In galvanometers, either of the sine or tangent type, the magnetic field produced by the electric circuit is compared with the earth’s horizontal field, the strength of which is determined independently. Further, as the strength of artificial magnets cannot be regarded as truly constant, and the earth’s field is subject to diurnal and secular variations, this class of measurement is not ideal. In the electrodynamic class of measurement the mutual action between two or more coils carrying current takes the form of a torque, as in electrodynamometers, or a direct force, as in current weighers. In electrodynamometers the torque may be measured with a bifilar suspension, the torsion of a wire or spring, or by means of a gravity balance. Current weigher measurements are almost always made by direct comparison with gravity, which is believed to be constant, and is known to a higher degree of accuracy than the strengths of any magnet or magnetic field that has yet been measured.

V. Experimental determination of the velocity of white and of coloured light

1882 ◽  
Vol 173 ◽  
pp. 231-289 ◽  
Keyword(s):  
Experimental Determination ◽  
Late Professor ◽  
Velocity Of Light ◽  
Accurate Knowledge ◽  
Number Of Teeth ◽  
Propagation Of Light ◽  
The Mean ◽  
Electro Magnetic ◽  
Made In

It is remarkable that, although the importance of an accurate knowledge of the velocity of light has been very generally appreciated, no attempt has hitherto been made in this country to measure that velocity by experiment. Our own experiments date from many years back, but we have been prevented by various interruptions to our work from giving a result which could lay claim to the greatest accuracy. In 1878 we made at Pitlochry, in Perthshire, between 600 and 700 observations, but the toothed wheel which was made for us not having the number of teeth in it which we had ordered, we were not able to eliminate perfectly certain unknown quantities occurring in the formulæ, and we felt that it would be better to wait until we could give a result in which we had perfect confidence. At the same time we resolved so to alter our apparatus that we should not have to depend upon the mean of a very large number of experiments to give us a good result, but that each observation should give us an accurate measurement, free from all doubt. This has now been accomplished by the experiments conducted in 1880-81 between Kelly House, Wemyss Bay, and the hills behind Innellan, across the mouth of the River Clyde. The chief importance of a determination of the velocity of light is that it gives us the means, considered by many to be the best means, of determining the solar parallax, by combining the result with the constant of aberration determined by astronomers. The investigation has also acquired a further interest from the speculations of the late Professor Clerk Maxwell, according to which the propagation of light is an electro-magnetic phenomenon, and its velocity should be the same as that of the propagation of an electro-magnetic displacement.

Spectroscopic Method for Measuring Surface Temperature That is Independent of Material Emissivity, Surrounding Radiation Sources, and Instrument Calibration

1994 ◽  
Vol 48 (2) ◽  
pp. 265-270 ◽  
Author(s):  
James R. Markham ◽  
Philip E. Best ◽  
Peter R. Solomon
Keyword(s):  
Surface Temperature ◽  
Optical Measurement ◽  
Spectroscopic Method ◽  
Instrument Calibration ◽  
Measuring Surface ◽  
Radiation Sources ◽  
Infrared Spectrometer ◽  
Electro Magnetic ◽  
The Fourier Transform

A novel optical measurement technique for the in situ determination of surface temperature is presented. The technique employs modulation of the object temperature by an energy source of high intensity, such as a laser. By modulation of the temperature at the point from which the emitted spectrum of electro-magnetic radiation is being monitored, routine calculations involving the observed modulated component of the radiation spectrum will determine the temperature and, for some conditions, emissivity. The region to be measured is thus defined by the intersection of the laser and the beam which enters the collection optics of the Fourier transform Infrared spectrometer. Analysis of the modulated radiation results in a temperature determination which is independent of material emissivity, surrounding radiation sources, and instrument calibration for optical path.

scholarly journals On a method of estimating distances at sea in fog or thick weather

1916 ◽  
Vol 92 (637) ◽  
pp. 170-175
Keyword(s):  
Subsequent Paper ◽  
Electro Magnetic ◽  
Magnetic Disturbances ◽  
Scientific Advances

The problem of estimating distances at sea in fog or thick weather is obviously one of much importance to navigation. Notwithstanding the more perfect means of communication between ship and shore, or between ship and ship, which recent scientific advances have secured, and which are at the command of the more important ships and lighthouse stations at the present time, I can find no reference to the fact that these improved means of communication suffice to solve the problem referred to under a great variety of circumstances. In the present paper I shall confine myself to the determination of distance between ship and shore. In a subsequent paper I hope to discuss the application of the methods involved to finding the distance between ship and ship, and thereby lessening risk of collision. The method I have to propose is based generally on the differing velocities of signals in different media: (1) luminous or "wireless" signals (electro-magnetic disturbances) may be regarded as instantaneously propagated over the distance concerned; (2) submarine sounds- e. g. , bell-storkes under water-travel in the water at the rate of about 1400 metres, or 4700 feet per second; (3) aërial sounds move at the rate of about 330 metres, or 1100 feet per second. Explosive signals travel somewhat faster in water and air.

Nichtlineare Spinorgleichungen und affiner Zusammenhang

1964 ◽  
Vol 19 (7-8) ◽  
pp. 825-827
Author(s):  
G. Braunss
Keyword(s):  
Lorentz Transformation ◽  
Space Time ◽  
Linear Term ◽  
Pauli Equation ◽  
Non Linear ◽  
The Matrix ◽  
Lorentz Condition ◽  
Electro Magnetic ◽  
Point To Point

It is shown that the non-linear term of the HEisENBERG-PAULi-equation can be interpreted as torsion of space-time in the following way. The wavefuinction is subjected to a (non-rigid) LORENTZ-transformation varying from point to point: ψ = Sψ'. If the matrix S=S(x) is chosen so that it satisfies the equation γλ(∂S/∂xλ) S-1+l2γλγ5 ψ̅ γλγ5ψ=0, than the non-linear term of the H.-P.-equation vanishes in the system x'; i. e.with (∂xλ/∂xμ′) γμ=S-1 γλ S one has 0=γλ(∂ψ/∂xλ) +l2γλγ5 ψ ψ̅ γλ γ5 ψ ≡ S γμ (∂ψ'/∂xμ′). This result holds also in the case where the H.-P.-equation contains still a term with γλ ψ̅ γλ ψ and/or γλ Αλ (Aλ = electro-magnetic potential), provided Aλ satisfies the LoRENTz-condition ∂Aλ/∂xλ=0. The proof is a follows: Taking a representation of S in the DIRAC-ring, the equation which determines S splits into 8 equations. Between these equations there exist 2 identities (which correspond to the PAULI—GuRSEY-transformation resp. LoRENTz-condition); so one finally has 6 equations for the determination of the 6 parameters of S.

Determination of the Dynamic Characteristics of Machine Tool Structures

1969 ◽  
Vol 184 (1) ◽  
pp. 943-960 ◽  
Author(s):  
I. Chowdhury ◽  
M. M. Sadek ◽  
S. A. Tobias
Keyword(s):  
Machine Tool ◽  
Milling Machine ◽  
Response Data ◽  
Machine Tool Structure ◽  
Milling Machines ◽  
Machine Tool Structures ◽  
Machine Spindle ◽  
Electro Magnetic ◽  
Vibration Tests

The ‘operative harmonic response locus’ of a machine tool structure, which is required for the prediction of machining stability, must be determined by vibration tests carried out under conditions which simulate closely those arising during cutting. This requires that such tests be performed while the tool or the workpiece spindle is rotating, the vibrations being excited by a small harmonic force superimposed on a large constant pre-load. It is not possible to satisfy these conditions with vibrators working on electro-dynamic or electro-hydraulic principles and so an electro-magnetic vibrator was designed and developed to meet the above requirements (2). This excitor can be used with all types of machine tools, but in the present investigation its application is restricted to lathe and horizontal milling machines. The effects of the rotational speed of the lathe spindle and milling machine spindle, of the exciting force amplitude and of the pre-load magnitude and direction on the response data, are investigated. It is found that the lathe structure behaves in a linear fashion whereas the behaviour of the milling machine is non-linear.

XII.—On a New Method of Measurement of Minute Alternating Currents

1931 ◽  
Vol 50 ◽  
pp. 166-174 ◽  
Author(s):  
D. F. Martyn
Keyword(s):  
Magnetic Field ◽  
Alternating Current ◽  
New Method ◽  
Electro Magnetic Field ◽  
Highly Sensitive ◽  
Method Of Measurement ◽  
Electro Magnetic ◽  
Sensitive Method ◽  
Plate Current

SummaryA highly sensitive method of measuring alternating currents of the order of microamperes and of any frequency is described. The current to be measured is passed through the filament of a diode valve. The main heating current of this valve is supplied by an independent oscillator working at the frequency of the current under measurement. The change in the plate current of the valve is measured, thus indicating the amplitude of the alternating current being measured. Theoretical and practical details of the methods of working are given and particulars of the method by which the calibration was tested. It is suggested that the method is particularly applicable to the determination of electro-magnetic field strengths by measuring the currents induced in an aerial.

Sign in / Sign up

Export Citation Format

Share Document