scholarly journals On a method of comparing mutual inductance and resistance by the help of two-phase alternating currents

1908 ◽  
Vol 81 (549) ◽  
pp. 450-452
Keyword(s):  
National Physical Laboratory ◽  
Mutual Inductance ◽  
Two Phase ◽  
Physical Laboratory ◽  
Absolute Measure ◽  
Commutator Method ◽  
Capacity Of A Condenser ◽  
The Ideal

A standard mutual inductance, after the design recently described by the writer, has now been constructed at the National Physical Laboratory. As the details of its construction will be published later, it is sufficient here to mention that its value calculated from the dimensions is 10.0178 millihenries. It forms an extremely accurate standard, against which both mutual and self inductances can be readily tested. In addition to this, it affords a means of obtaining values of resistance coils in absolute measure, and thus evaluating the ohm. This can be done in an indirect way by finding the capacity of a condenser in terms of resistance and time by Maxwell’s Commutator Method, and in terms of resistance and mutual inductance by Heydweiller’s modification of Carey Foster’s method. The comparison of resistance with mutual inductance can, however, be made far more simply and directly by the use of two-phase alternating currents in the method which I proceed to describe. I shall first take the ideal simple case, and afterwards notice some of the difficulties that may arise in practice. (2) Theory of the Medhod. In fig. 1 let M be the mutual inductance (a small fraction of it being adjustable) and R the resistance; and let A cos pt and B sin pt be currents in quadrature, e. g ., from a two-phase alternator or a phasesplitting device. Let G be a vibration galvanometer tuned to frequency n where p = 2 πn .

scholarly journals On the determination of the absolute unit of resistance by alternating current methods

1912 ◽  
Vol 87 (597) ◽  
pp. 391-414 ◽  
Keyword(s):  
Lower Order ◽  
Alternating Current ◽  
National Physical Laboratory ◽  
Mutual Inductance ◽  
Electrical Circuits ◽  
Physical Laboratory ◽  
Absolute Measure ◽  
The Absolute ◽  
Set Up

1. Introductory .—Recently at the National Physical Laboratory we have constructed a standard of mutual inductance of novel type, whose value has been accurately calculated from the dimensions. This inductance has formed the basis for the determination of the unit of resistance in absolute measure by two different methods, in both of which alternating current is employed. Although there is no doubt that the accuracy attainable by these methods could be increased by greater elaboration of the apparatus used, the results already obtained seem to be of sufficient interest to warrant publication. It should be mentioned that the accuracy here aimed at was of a considerably lower order than that contemplated in the determination of the ohm by the Lorenz apparatus which is at present being carried out in the laboratory. For the experiments here described, no apparatus was specially constructed, but use was made of instruments which had already been designed and set up for the measurement of inductance and capacity. I shall first give a brief description of the standard inductance and then pass on to the methods and results. 2. Standard Mutual Inductance .—The design of the mutual inductance has already been described. The electrical circuits have the form and arrange­ment shown in section in fig. 1.

scholarly journals On a standard of mutual inductance

1907 ◽  
Vol 79 (532) ◽  
pp. 428-435 ◽  
Keyword(s):  
National Physical Laboratory ◽  
Mutual Inductance ◽  
Electrical Measurements ◽  
Working Standard ◽  
Standard Unit ◽  
Magnetic Testing ◽  
Physical Laboratory ◽  
Rayleigh Method ◽  
Geometrical Dimensions ◽  
Commutator Method

1. Introductory .—In many electrical measurements, such as those of capacity and inductance, as well as in the magnetic testing of iron, an accurately known standard of mutual inductance is of great value. It is sometimes convenient to derive such a standard from the standard unit of resistance, and this may be done in several ways, for example, by the well-known method of the ballistic galvanometer; or by Carey Foster’s method the mutual inductions may be tested against a condenser whose capacity has been found in terms of resistance and frequency by Maxwell’s commutator method; or it may be obtained directly in similar terms by the help of an unknown inductance by the Hughes-Rayleigh method. In the National Physical Laboratory I have used both of these latter methods (with the help of a vibration galvanometer) to obtain a working standard of mutual inductance. But this procedure is somewhat illogical, seeing that the unit of resistance has been itself commonly determined by the aid of mutual inductances calculated from the dimension of the coils or other conductors used; thus for the highest accuracy it is desirable to revert to a standard whose value can be determined solely from the geometrical dimensions. Accordingly, some eighteen months ago, I took in hand the investigation of a suitable design for such a standard, and I proceed to describe the result at which I arrived.

scholarly journals Calculation of a primary standard of mutual inductance of the Campbell type and comparison of it with the similar N. P. L. standard

1922 ◽  
Vol 101 (711) ◽  
pp. 315-332 ◽  
Keyword(s):  
Primary Standard ◽  
Single Layer ◽  
Alternating Current ◽  
National Physical Laboratory ◽  
Mutual Inductance ◽  
Secondary Coil ◽  
Physical Laboratory

The standard mutual inductance devised and designed by Mr. A. Campbell and constructed in 1907-8 at the National Physical Laboratory has been one of the foundations of our alternating current measurements since that date. It will be sufficient here to note that the special feature in the design of the Campbell type of mutual inductance consists in a primary single-layer winding, so proportioned that the field due to it is practically zero over the region occupied by the secondary coil. By this means the dimensions of the secondary coil are rendered relatively unimportant, so that it may be an overwound many-layer winding, whereby a suitably large value of mutual inductance may be obtained.

scholarly journals 75th Foundation Day of CSIR-National Physical Laboratory: Celebration of Achievements in Metrology for National Growth

MAPAN ◽  
2021 ◽  
Author(s):  
Sanjay Yadav ◽  
Goutam Mandal ◽  
V. K. Jaiswal ◽  
D. D. Shivagan ◽  
D. K. Aswal
Keyword(s):  
National Physical Laboratory ◽  
Physical Laboratory ◽  
National Growth

scholarly journals Two-phase CFD simulation of the monodyspersed suspension hydraulic behaviour in the tank apparatus from a circulatory pipe

2008 ◽  
Vol 10 (1) ◽  
pp. 22-27 ◽  
Author(s):  
Roch Plewik ◽  
Piotr Synowiec ◽  
Janusz Wójcik
Keyword(s):  
Cfd Simulation ◽  
Fluidised Bed ◽  
Cfd Simulations ◽  
Two Phase ◽  
Hydraulic Behaviour ◽  
Hydraulic Conditions ◽  
The One ◽  
Cfd Method ◽  
Multi Phase ◽  
The Ideal

Two-phase CFD simulation of the monodyspersed suspension hydraulic behaviour in the tank apparatus from a circulatory pipe The hydrodynamics in fluidized-bed crystallizers is studied by CFD method. The simulations were performed by a commercial packet of computational fluid dynamics Fluent 6.x. For the one-phase modelling (15), a standard k-ε model was applied. In the case of the two-phase flows the Eulerian multi-phase model with a standard k-ε method, aided by the k-ε dispersed model for viscosity, has been used respectively. The collected data put a new light on the suspension flow behaviour in the annular zone of the fluidised bed crystallizer. From the presented here CFD simulations, it clearly issues that the real hydraulic conditions in the fluidised bed crystallizers are far from the ideal ones.

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