scholarly journals Experimental researches in electricity

1837 ◽  
Vol 3 ◽  
pp. 91-93
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
The Other ◽  
Great Length ◽  
Electrical Currents ◽  
Electric Current Passing ◽  
Electrical Condition ◽  
The Moment ◽  
Electrical Induction ◽  
Experimental Researches

This paper is divided into four parts: the first being on the Induction of Electric Currents; the second, on the Evolution of Electricity from Magnetism; the third, on a new Electrical Condition of Matter; and the fourth, on Arago’s Magnetic Phænomena. The author defines electrical induction to be the power which electrical currents possess of inducing any particular state upon matter in their immediate neighbourhood. A great length of copper wire, 1-20th of an inch in diameter, was wound round a cylinder of wood so as to compose two helices, the coils of which were intermixed, but prevented from touching each other by interposed threads of twine and calico. One helix was connected with a voltaic battery, and the other with a galvanometer. No effect was perceived on the latter, with a battery of 10 plates; a slight effect only with one of 100 plates; and a distinct deflection of the needle of the galvanometer occurred when the contact was made with a battery of 120 plates. While the contact was preserved, the needle returned to its natural position, and was unaffected by the electric current passing through the wire connected with the battery; but on breaking the connexion, the needle of the galvanometer was again deflected, but in a direction contrary to that of its former deflection. Hence it is inferred that the electric current sent by the battery through one wire, induced a similar current through the other wire, but only at the moment the contact was made; and a current in the contrary direction when the passage of the electricity was suddenly interrupted. These transitory currents, resembling waves, were found to be capable of magnetizing needles placed within the helix. Collateral currents, either in the same or in opposite directions, exert no permanent inductive power on each other.

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.

XIII. Introductory research on the Induction of magnetism by electrical currents

1856 ◽  
Vol 146 ◽  
pp. 287-295
Keyword(s):  
Copper Wire ◽  
The Other ◽  
Electrical Currents ◽  
Molecular Changes ◽  
General Law ◽  
Linear Dimensions ◽  
The Subject ◽  
Different Dimensions ◽  
Different Diameters ◽  
Experimental Researches

The researches of Jacobi and Lenz led them some years ago to the announcement as a law, that when two bars of iron of different diameters but equal to one another in length and surrounded with coils of wire of the same length carry equal streams of electricity, the magnetism developed in the bars is proportional to their respective diameters. Experiments which I made about the same time threw doubts on my mind as to the general accuracy of the above proposition, for I found that the magnetism induced in straight bars of a variety of dimensions varying from ⅓ to 1 inch in diameter, and from 7 inches to one yard in length, was nearly proportional to the length of the wire and the intensity of the current it conveyed, irrespectively of the shape or magnitude of the bars. The valuable experimental researches which have recently been made by Weber, Robinson, Müller, Dub and others, refer chiefly to the attraction of the keeper or submagnet, and are not calculated to confirm or disprove either of the above propositions; and the correct view is probably that of Professor Thomson, who considers both of them as corollaries (applying to the particular conditions under which the experiments were made) of the general law, that “similar bars of different dimensions, similarly rolled with lengths of wire proportional to the squares of their linear dimensions and carrying equal currents, cause equal forces at points similarly situated with reference to them*.” I have been induced to undertake some further experiments with an endeavour to elucidate the subject, and also to open the way to the investigation of the molecular changes which occur during magnetization. I procured four iron bars one yard long and of the respective diameters and 1/6, ¼, ½ and 1 inch, their weights being 1736, 3802, 14560, and 55060 grs. Each bar was wound with 56 feet of copper wire 1/40th of an inch in diameter covered with silk, the number of convolutions being 1020, 712, 388, and 207 respectively. The smallest bar was closely covered throughout its entire length, but on account of the larger surface of the other bars the coils had to be distributed upon them as evenly as possible. Four other bars were also procured of the same diameters as the above. They were however twice as long, weighing 3500, 7624, 29944, and 108574 grs., and were wrapped with double the length of wire, forming 2060, 1435, 768, and 418 convolutions respectively.

scholarly journals IV. On the development of electric currents by magnetism and heat

1869 ◽  
Vol 17 ◽  
pp. 265-267
Keyword(s):  
Copper Wire ◽  
Glass Tube ◽  
Rubber Band ◽  
The Other ◽  
Internal Diameter ◽  
External Diameter ◽  
Thin Glass ◽  
Iron Wire ◽  
It Flexibility ◽  
Electric Current Passing

I have devised the following apparatus for demonstrating a relation of current electricity to magnetism and heat. A A, fig. 3, is a wooden base, upon which is supported, by four brass clamps, two, B, B, on each side, a coil of wire, C; the coil is 6 inches long, 1½ inch external diameter, and ⅜ of an inch internal diameter, lined with a thin glass tube; it consists of 18 layers, or about 3000 turns of insulated copper wire of 0·415 millim. diameter (or size No. 26 of ordinary wire-gauge); D is a permanent bar-magnet held in its place by the screws E, E, and having upon its poles two flat armatures of soft iron, F, F, placed edgewise. Within the axis of the coil is a straight wire of soft iron, G, one end of which is held fast by the pillar-screw H, and the other by the cylindrical binding-screw I; the latter screw has a hook, to which is attached a vulcanized india-rubber band, J, which is stretched and held secure by the hooked brass rod K and the pillar-screw L. The screw H is surmounted by a small mercury cup for making connexions with one pole of a voltaic battery, the other pole of the battery being secured to the pillar-screw M, which is also surmounted by a small mercury cup, and is connected with the cylindrical binding-screw I by a copper wire with a middle flattened portion O to impart to it flexibility. The two ends of the fine wire coil are soldered to two small binding-screws at the back; those screws are but partly shown in the sketch, and are for the purpose of connexion with a suitable galvanometer. The armatures F, F are grooved on their upper edges, and the iron wire lies in these grooves in contact with them; and to prevent the electric current passing through the magnet, a small piece of paper or other thin non-conductor is inserted between the magnet and one of the armatures. The battery employed consisted of six Grove’s elements (arranged in one series), with the immersed portion of platinum plates about 5 inches by 3 inches; it was sufficiently strong to heat an iron wire 1·03 millim. diameter and 20·5 centims. long to a low red heat.

scholarly journals Experimental researches in electricity. Twenty-fourth series. On the possible relation of gravity to electricity

1851 ◽  
Vol 5 ◽  
pp. 994-995 ◽  
Keyword(s):  
Electric Current ◽  
The Other ◽  
Electric Force ◽  
The Earth ◽  
Gravity And Magnetic ◽  
Experimental Relation ◽  
Other Substances ◽  
Fourth Series ◽  
Experimental Researches ◽  
Electric Action

Under the full persuasion that all the forces of nature are mutually dependent, and often, if not always, convertible more or less into each other, the author endeavoured to connect gravity and magnetic or electric action together by experimental results, and though the conclusions were, when cleared from all error, of a negative nature, he still thinks that the principle followed and the experiments themselves deserve to be recorded. Considering that some condition of the results produced by gravity ought to present itself, having a relation to the dual or antithetical character of the magnetic or electric forces, it seemed to the author that the approximation of two gravitating bodies towards each other, and their separation, were the only points which offered this kind of coincidence; and therefore, using the earth as one gravitating body, he employed a cylinder of metal, glass, resins, or other substances, as the other, and endeavoured to ascertain when the latter was allowed to fall, being surrounded by a helix of wire, whether any electric current was generated. Sometimes the cylinder was allowed to fall through the helix; at other times with the helix; and occasionally the helix was made the falling body. But when the various sources of error which sprung up were gradually removed, no traces of electric action remained which could be referred to the power of gravity. In order to obtain a greater effect, an aparatus was employed (being nearly that, used in the 23rd Series of these Researches) by which the effect of raising a body from the earth could be combined with that of a falling body by the fit use of commutators (if any action at all were produced). The apparatus was very good, and gave exceedingly delicate results, as was shown by other consequences of its action; but in respect of gravity it produced no effect whatever. Notwithstanding his failure in obtaining any experimental relation between gravity and magnetic or electric force, the author still expresses his conviction that there is a relation, and his hopes that it may be hereafter practically demonstrated.

Experimental researches in electricity. Atmospheric magnetism, continued. Twenty-seventh series

1851 ◽  
Vol 5 ◽  
pp. 1000-1001
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
Average Temperature ◽  
Magnetic Forces ◽  
The North ◽  
The Earth ◽  
Axis Parallel ◽  
The Difference ◽  
Experimental Researches ◽  
Lines Of Force

In order to obtain an experimental representative of the action of the atmosphere when heated above or cooled below the average temperature, the author employed a ring helix of covered copper wire, through which an electric current was passed. The helix was about one inch and a half in diameter, and having the well-known system of magnetic forces, was placed with its magnetic axis parallel to a free needle: when its position was such that a needle within the ring would point with the north end downward, then the effect in deflecting the surrounding lines of force of the earth was considered as like that of a relatively paramagnetic mass of air: and when its position was reversed, its action was representative of that of a heated or relatively diamagnetic mass of air. Bringing this helix into the vicinity of small magnetic needles, suspended either freely, or so as to show declination or inclination, the planes of action or indifference as regards the power of deflecting the lines of force and the needle were observed. When the needle can move only in one plane, there are four quadrants, formed (in the case of the declination needle) by the intersection of the planes of the magnetic equator and meridian. When in these planes there is no deflection at the needle, but when in the quadrants there is, and in opposite directions in the neighbouring quadrants. As the lines of force are held in and by the earth, so these experiments were repeated with a needle in near vicinity to a magnet, and the difference of effect is pointed out: then the extent to which these results are applicable to those of the earth is considered, and their utility in guiding the inquirer.

scholarly journals Description of the electro-magnetic clock

1843 ◽  
Vol 4 ◽  
pp. 249-250 ◽  
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
The Other ◽  
Maximum Effect ◽  
Magnetic Coils ◽  
Small Disc ◽  
The Difference ◽  
Electro Magnetic ◽  
Fixed End ◽  
Metallic Parts

The object of the apparatus forming the subject of this communication, is stated by the author to be that of enabling a single clock to indicate exactly the same time in as many different places, distant from each other, as may be required. Thus, in an astronomical observatory, every room may be furnished with an instrument, simple in its construction, and therefore little liable to derangement, and of trifling cost, which shall indicate the time, and beat dead seconds audibly, with the same precision as the standard astronomical clock with which it is connected; thus obviating the necessity of having several clocks, and diminishing the trouble of winding up and regulating them separately. In like manner, in public offices and large establishments, one good clock will serve the purpose of indicating the precise time in every part of the building where it may be required, and an accuracy ensured which it would be difficult to obtain by independent clocks, even putting the difference of cost out of consideration. Other cases in which the invention might be advantageously employed were also mentioned. In the electro-magnetic clock, which was exhibited in action in the Apartments of the Society, all the parts employed in a clock for maintaining and regulating the power are entirely dispensed with. It consists simply of a face with its second, minute and hour hands, and of a train of wheels which communicate motion from the arbor of the second’s hand to that of the hour hand, in the same manner as in an ordinary clock train; a small electro-magnet is caused to act upon a peculiarly constructed wheel (scarcely capable of being described without a figure) placed on the second’s arbor, in such manner that whenever the temporary magnetism is either produced or destroyed, the wheel, and consequently the second’s hand, advances a sixtieth part of its revolution. It is obvious, then, that if an electric current can be alternately established and arrested, each resumption and cessation lasting for a second, the instrument now described, although unprovided with any internal maintaining or regulating power, would perform all the usual functions of a perfect clock. The manner in which this apparatus is applied to the clocks, so that the movements of the hands of both may be perfectly simultaneous, is the following. On the axis which carries the scape-wheel of the primary clock a small disc of brass is fixed, which is first divided on its circumference into sixty equal parts ; each alternate division is then cut out and filled with a piece of wood, so that the circumference consists of thirty regular alternations of wood and metal. An extremely light brass spring, which is screwed to a block of ivory or hard wood, and which has no connexion with the metallic parts of the clock, rests by its free end on the circumference of the disc. A copper wire is fastened to the fixed end of the spring, and proceeds to one end of the wire of the electro-magnet; while another wire attached to the clock-frame is continued until it joins the other end of that of the same electromagnet. A constant voltaic battery, consisting of a few elements of very small dimensions, is interposed in any part of the circuit. By this arrangement the circuit is periodically made and broken, in consequence of the spring resting for one second on a metal division, and the next second on a wooden division. The circuit may be extended to any length ; and any number of electro-magnetic instruments may be thus brought into sympathetic action with the standard clock. It is only necessary to observe, that the force of the battery and the proportion between the resistances of the electro-magnetic coils and those of the other parts of the circuit, must, in order to produce the maximum effect with the least expenditure of power, be varied to suit each particular case. In the concluding part of the paper the author points out several other and very different methods of effecting the same purpose; and in particular one in which Faraday’s magneto-electric currents are employed, instead of the current produced by a voltaic battery: he also describes a modification of the sympathetic instrument, calculated to enable it to act at great distances with a weaker electric current than if it were constructed on the plan first described.

scholarly journals Experimental researches in electricity. Ninth series

1837 ◽  
Vol 3 ◽  
pp. 318-319
Keyword(s):  
Electric Current ◽  
Single Pair ◽  
Fine Wire ◽  
Considerable Length ◽  
Good Conductor ◽  
Series Of Experiments ◽  
The Wire ◽  
The Moment ◽  
Experimental Researches ◽  
A Current

In the series of experiments which are detailed in this paper, the author inquires into the causes of some remarkable phænomena relating to the action of an electric current upon itself, under certain circumstances, whereby its intensity is highly exalted, and occasionally increased to ten, twenty, or even fifty times that which it originally possessed. For the production of this effect, the principal condition is that the current traverse a considerable length of a good conductor, such as a long wire; more especially if this wire be coiled in the form of a helix; and the effect is still farther augmented when this helix is coiled round a cylinder of soft iron, constituting an electro-magnet. The evidence on which these conclusions are founded is the following. If an electromotor, consisting of a single pair of zinc and copper plates, have these metals connected by a short wire dipping into cups of mercury, the electric spark consequent upon either forming or breaking the circuit is so slight as to be scarcely perceptible; but if a long wire be employed as the medium of connexion, a bright spark is obtained on breaking the contact. If the wire be coiled in a helix, the spark is still brighter; and if a core of soft iron be placed within the helix, the spark, at the moment of disjunction, is more brilliant than in any of the former cases: and the higher intensity of the current is also manifested by the occurrence of a shock, at the same moment, to a person who grasps with wetted hands the two ends of the wire; whereas no such effect, nor even any sensible impression on the tongue, is produced by the electromotor, when a short wire is employed. All these effects of exaltation are produced at a time when the actual current of electricity from the electromotor is greatly diminished; as the author shows by many experiments on the ignition of a fine wire, and the deflection of a galvanometer. He also proves that the effects of the spark and the shock, at the moment of disjunction of a long wire, are due to a current far more powerful than that which passes through the short wire at the same instant; or indeed than that which passes through either the long or the short wire at any other instant of time than when the disjunction takes place.

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.

On the increase in resistance to the passage of an electric current produced on certain wires by stretching

1878 ◽  
Vol 26 (179-184) ◽  
pp. 401-410
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
Lower Extremities ◽  
The Other ◽  
Platinum Wire ◽  
Sliding Scale ◽  
The Mean ◽  
The Wire ◽  
Two Sides ◽  
Permanent Increase

The object of this inquiry was (1) to determine the relation between increased resistance to the passage of an electric current and stretching-force; (2) to ascertain how much of the increased resistance in each case is produced by mere increase of length and diminution of section. In order to determine the increase of resistance from stretching, the wires were each divided into two parts about 14 feet or more in length. One end of each part was fastened to a stout hook, firmly fixed into a block of wood, the two hooks used being about 8 inches apart, and the block of wood in which they were fixed securely fastened across two strong uprights, which were placed resting against the wall, so that the weights attached to the wires might swing clear of the table on which the uprights were placed. A loop was made at the other end of each part of the wire, and to this the weights were attached by means of strong hooks. The two parts of the wire were joined at the top, about 2 inches below each hook, by a piece of copper wire, which was securely soldered on to each part of the wire, so as to connect them; and toward the lower extremities of the two parts, about 5 inches above the points of attachment of the weights, two copper wires were soldered so as to connect the wires with a Wheatstone’s bridge. The increase of resistance of the wires was measured by means of a sliding scale of platinum wire divided into millimetre divisions, each equal to ·00166 ohm. As the object was to obtain the temporary and not the permanent increase of resistance (which permanent increase was found more or less with al the wires), weights slightly heavier than those intended to be used were first put on and taken off. Afterwards the wire was balanced as nearly as possible by German-silver wire, without the sliding scale, and then very exactly with the sliding scale, which was connected with one of two resistance-coils of 100 ohms each, which formed the other two sides of the bridge. The weights used were then carefully put on to the wires and the increase of resistance measured by means of the sliding scale the weights were next taken off again, and the sliding scale used for balancing once more. If there was any slight difference, as sometimes occurred, between the readings of the sliding scale before the weights were put on and after they were taken off, the mean of the two readings was taken.

scholarly journals Experimental researches in electricity—Second series

1837 ◽  
Vol 3 ◽  
pp. 95-97
Keyword(s):  
Electrical Machines ◽  
Electric Currents ◽  
Electrical Currents ◽  
The Earth ◽  
The Subject ◽  
The Moment ◽  
Magnetic Poles ◽  
Experimental Researches ◽  
Contrary Direction

The success of the author in exhibiting the evolution of electricity by induction from ordinary magnets, led him to conclude that similar effects might be obtained from the magnetism of the earth, and even to an extent that might render it available in the construction of new electrical machines. These expectations have been fully realized; and the researches which establish the influence of terrestrial induction in giving rise to electrical currents, form the subject of this second paper. Whenever a hollow helix, the terminal wires of which were connected with those of a galvanometer, and which inclosed a cylinder of soft iron, was held with its axis in the line of the magnetic dip, and suddenly inverted, the evolution of electric currents was immediately rendered sensible by the deflection of the needle of the galvanometer; a deflection in the contrary direction being produced the moment the helix was again inverted, so as to recover its first position. The same effect resulted from the simple introduction of the iron cylinder into, or its removal out of, the helix; evidently in consequence of the magnetism acquired by position with relation to the magnetic poles of the earth. When a cylindric magnet was substituted for the soft iron, the same phænomena, obviously ascribable to terrestrial induction, were in either case observed. Similar but more feeble indications of the same effect were obtained by inverting the helix alone, without its association with any ferruginous body whatever.

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