scholarly journals The Magnetism of the Earth. A Lecture on the Distribution and Direction of the Earth's Magnetic Force at the Present Time: The Changes in Its Elements, and on Our Knowledge of the Causes

1877 ◽  
Vol 22 (3) ◽  
pp. 188
Author(s):  
F. J. Evans
Keyword(s):  
Magnetic Force ◽  
The Earth

scholarly journals Experimental researches in electricity: Twenty-ninth series

1854 ◽  
Vol 6 ◽  
pp. 165-168 ◽  
Keyword(s):  
Magnetic Force ◽  
Present Series ◽  
The Earth ◽  
Experimental Researches ◽  
Thick Wire

In the present series of researches the author endeavours in the first place to establish the principles he announced in the last, with regard to the definite character of the lines of magnetic force, by results obtained experimentally with the magnetic force of the earth. For this purpose he reverts to the thick wire galvanometer before described, and points out the precautions respecting the cleanliness of the coils, the thickness and shortness of the conductors, the perfect contacts, effected either by soldering or cups of mercury; and marks the value of double observations, i. e. observations afforded on both sides of zero.

scholarly journals The transmission of electric waves round the Earth

1919 ◽  
Vol 95 (673) ◽  
pp. 546-563 ◽  
Keyword(s):  
Numerical Computation ◽  
Magnetic Force ◽  
Complete Solution ◽  
Angular Distance ◽  
Actual State ◽  
Absolute Value ◽  
Conducting Sphere ◽  
The Earth ◽  
State Of Affairs ◽  
Electric Waves

On the hypothesis that the Earth consists of an imperfectly conducting sphere surrounded by infinite homogeneous dielectric, I have recently obtained a complete solution (in a form adapted for numerical computation) of the problem of determining the effect at a distant point of the Earth’s surface due to a Hertzian oscillator emitting waves of a definite frequency. Previous investigators had obtained approximations (some of which were incorrect) to the dominant terms of the series which represents the effect due to the Earth, but the earlier approximations cease to be valid in the neighbourhood of the antipodes of the transmitter. On this hypothesis the absolute value of the Hertzian function (with the time-factor suppressed) is roughly proportional to (sin θ ) -½ exp (- 23⋅94 λ -⅓ θ ), where λ is the wavelength measured in kilometres, θ and is the angular distance from the transmitter. When θ is nearly equal to π, the factor (sin θ ) -½ has to be suppressed. This formula does not agree with results obtained experimentally. The numerical factor 23⋅94 is much too large, so that, as θ increases, the magnetic force decays much less rapidly than the theory indicates; and it has also been suggested on experimental grounds that the actual state of affairs is represented much more closely when the factor λ -⅓ is replaced by the factor λ -½ .

GROUND-BASED EXPERIMENTS TO DETECT GRAVITO-MAGNETIC FORCE

2013 ◽  
Vol 23 ◽  
pp. 115-124
Author(s):  
HUI PENG
Keyword(s):  
Magnetic Force ◽  
Torsion Balance ◽  
Optic System ◽  
Magnetic Forces ◽  
The Earth ◽  
Rotation Of The Earth

Based on Maxwell-type linearized Einstein Eqs of gravity, new ground-base torsion balance experiments are proposed to detect gravito-magnetic forces due to the rotation of the Earth. An optic system is employed to enlarge the effects so that the predicted effects are measurable by the proposed ground-based experiments.

scholarly journals On the variable intensity of ter­restrial magnetism, and the influence of the aurora borealis upon it

1837 ◽  
Vol 3 ◽  
pp. 37-38
Keyword(s):  
Magnetic Force ◽  
The Sun ◽  
South Pole ◽  
Variable Intensity ◽  
Aurora Borealis ◽  
The North ◽  
The Earth ◽  
Northern Latitudes ◽  
Snow Storms ◽  
Magnetic Needle

The author gives the results of a series of observations on the vibrations of the magnetic needle, which he undertook last summer, for the purpose of ascertaining whether the intensity of its directive force is affected by the changes in the earth’s distance from the sun, or by its declination with respect to the plane of its equator. He observed that the magnetic intensity is subject to frequent variations, which are sometimes sudden, and of short duration. These anomalies he has been unable to refer to any obvious cause, except when they were accompanied by the appearance of the aurora borealis, which evidently affected the needle on many occasions. He also thinks that the vibrations of the needle became less rapid with a moist atmosphere, and more so when it was very dry. Changes of the wind and snow storms appeared also to be attended with fluc­tuations in the intensity of the magnetism. He endeavoured to ascertain whether there existed any decided and constant difference in the directive force of each pole; conceiving that, on the hypothesis of a central magnetic force, the north pole of the magnet would, in these northern latitudes, be acted upon with much greater energy than the south pole. From his observing that the relative intensity of the two poles is not always the same, he infers the probability of the earth’s magnetism being derived from the agency of electric currents existing under its surface as well as above it, and that the rapid fluctuations in its intensity are owing to meteorological changes. The author is led to conclude that the aurora borealis is an elec­trical phenomenon, and that it usually moves during the night nearly from north to south, and in an opposite direction during the day ; that it is of the nature of positive electricity; and that its elevation above the earth is much greater than a thousand, and perhaps thou­sands of miles.

scholarly journals The transmission of electric waves around the Earth's surface

1916 ◽  
Vol 92 (643) ◽  
pp. 493-500 ◽  
Keyword(s):  
General Formula ◽  
Magnetic Force ◽  
Wave Length ◽  
Angular Distance ◽  
Electric Force ◽  
Present Communication ◽  
The Earth ◽  
Perfect Conduction ◽  
Electric Waves

The value of the magnetic force at a point on the earth's surface, due to a simple oscillator placed on the surface with its axis normal to the surface, has been recently calculated by Love for a wave-length of 5 kilom. at certain distances from the oscillator. His results for the case of perfect conduction are the same as the corresponding series when the surface of the earth is supposed to be imperfectly conducting, The object of the present communication is to obtain the general formula for the case of imperfect conduction. Let r, θ, ϕ be the polar co-ordinates of a point, where r is its distance from the centre of the earth, θ its angular distance from the oscillator, E r , E θ , E ϕ the components of the electric force, and α, β, γ , the corresponding components of the magnetic force. Then, Since there is symmetry round the axis of the oscillator, α =0, β =0, γ =0; and throughout space outside the surface

The magneto-hydrodynamics of a rotating fluid and the earth’s dynamo problem

1963 ◽  
Vol 274 (1357) ◽  
pp. 274-283 ◽  
Keyword(s):  
Magnetic Force ◽  
Necessary Conditions ◽  
Fluid Velocity ◽  
Rotating Fluid ◽  
Rigid Boundary ◽  
Viscous Forces ◽  
Magnetic Forces ◽  
The Earth ◽  
The Magnetic Field

This paper discusses a rotating, incompressible fluid enclosed within a rigid boundary which is a surface of revolution. It is shown that if viscous forces are negligible, then, in the presence of magnetic fields, the fluid can execute slow, steady relative motions only if the magnetic force satisfies a constraint. In cylindrical polar co-ordinates this constraint can be written that is, the couple exerted by the magnetic forces on any cylinder of fluid coaxial with the axis of rotation must vanish. Furthermore, subject to certain restrictions on the shape of the container (which, for example, are fulfilled by a sphere but not by a cylinder), it is shown that if the field satisfies the above condition then the fluid velocity is completely determined by the instantaneous value of the magnetic field (together with that of the density if buoyancy forces are important). This velocity is such that the necessary conditions on the field will continue to be satisfied. An algorithm for the determination of the velocity is given and its application to the earth ’s dynamo problem is indicated.

A Vehicle Heading and Attitude Measurement System Based on Earth Magnetic Field Sensor

2012 ◽  
Vol 588-589 ◽  
pp. 1140-1143
Author(s):  
Hao Hu
Keyword(s):  
Magnetic Field ◽  
Magnetic Force ◽  
Magnetic Field Sensor ◽  
Measuring System ◽  
Attitude Measurement ◽  
Induced Voltage ◽  
The Earth ◽  
Earth Magnetic Field ◽  
Field Sensor ◽  
Magnetic Force Line

Measurement method is studied utilizing vertical gyroscopevertical gyroscopevertical gyroscope, static earth magnetic field sensor and CPU. According to electromagnetism induction law, when a wire loop incises the magnetic force line of the earth magnetic field, it will bring about the induction electromotive force, the earth magnetic field can be calculated by signal processing of induced voltage in measuring coil. A heading and attitude measuring system to vehicle are designed, the heading precision were raised. Experiment data states clearly the heading precision is not more than 0.5°. This system can be used to detect heading and attitude, and can be extended easily.

scholarly journals XI. Experimental researches in electricity.—Twenty-ninth series

1852 ◽  
Vol 142 ◽  
pp. 137-159 ◽  
Keyword(s):  
Electric Current ◽  
Magnetic Force ◽  
Equal Proportion ◽  
Magnetic Forces ◽  
The Earth ◽  
Fine Wire ◽  
Pass Through ◽  
Experimental Researches ◽  
Experimental Indication ◽  
Equal Power

3177- The proposition which I have made to use the induced magneto-electric current as an experimental indication of the presence, direction and amount of magnetic forces (3074.), makes it requisite that I should also clearly demonstrate the principles and develope the practice necessary for such a purpose; and especially that I should prove that the amount of current induced is precisely proportionate to the amount of lines of magnetic force intersected by the moving wire, in which the electric current is generated and appears (3082, 3109.). The proof already given is, I think, sufficient for those who may repeat the experiments; but in order to accumulate evidence, as is indeed but proper in the first announcement of such a proposition, I proceeded to experiment with the magnetic power of the earth, which presents us with a field of action, not rapidly varying in force with the distance, as in the case of small magnets, but one which for a given place may be considered as uniform in power and direction; for if a room be cleared of all common magnets, then the terrestrial lines of magnetic force which pass through it, have one common direction, being that of the dip, as indicated by a free needle or other means, and are in every part in equal proportion or quantity, i. e . have equal power. Now the force being the same everywhere, the proportion of it to the current evolved in the moving wire is then perhaps more simply and directly determined, than in the case where, a small magnet being employed, the force rapidly changes in amount with the distance. i. Galvanometer . 3178. For such experimental results as I now propose to give, I must refer to the galvanometer employed and the precautions requisite for its proper use. The instrument has been already described in principle (3123.), and a figure of the conductor which surrounds the needles, given. This conductor may be considered as a square copper bar, 0·2 of an inch in thickness, which passes twice round the plane of vibration of each of the needles forming the astatic combination, and then is continued outwards and terminates in two descending portions, which are intended to dip into cups of mercury. As both the needles are within the convolutions of this bar, an indicating bristle or fine wire of copper is fixed parallel to, and above them upon the same axis, and this, in travelling over the usual graduated circle, shows the place and the extent of vibration or swing of the needles below. The suspension is by cocoon silk, and in other respects the instrument is like a good ordinary galvanometer.

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