Experiments as to the Effect of the Electrical Conflict on the Magnetic Needle

Author: Hans Christian Oersted  | Date: 21 July 1820

Experiments as to the Effect of the Electrical Conflict on the Magnetic Needle

Hans Christian Oersted

The first experiments concerning the subject which I am undertaking to elucidate, were carried out in the lectures which I gave last winter on electricity, galvanism and magnetism. From these experiments it seemed to appear that the magnetic needle could be moved from its position by means of the galvanic apparatus, and that with a closed galvanic circuit, and not with an open one, as certain noted physicists in vain attempted several years ago. As these experiments, however, were made with rather weak apparatus, and on that account the manifestations obtained seemed hardly commensurate with the importance of the subject, I called my friend Esmarch to my aid in order to repeat and multiply the experiments with him by means of a large galvanic apparatus which we constructed together.

In the account of our experiments I pass over all such as, though they led to the discovery, really added nothing to the explanation of the matter when once it was discovered, and confine myself to those from which the nature of the subject plainly appears.

The galvanic apparatus of which we made use consists of 20 rectangular copper cells, each 12 inches long by 12 deep, and 2 1/2 inches wide, and each provided with two strips of copper, so inclined as to support the copper bar which holds the zinc plate floating in the fluid of the adjoining cell. The water with which the cells were filled was mixed with 1–60 of its weight of sulphuric acid and an equal amount of nitric acid; the immersed part of the zinc plate in each cell was 10 inches square. Smaller apparatus than this may be used, provided it is capable of bringing the wire to a glow.

Imagine the two opposite ends of the galvanic apparatus united by a metal wire. This I shall call, for brevity, the connecting conductor, or the connecting wire: but the action which takes place in and around this connecting conductor I shall designate as the electrical conflict.

(1) Bring a straight piece of this connecting wire into a horizontal position over an ordinary freely moving magnetic needle so that the two will be parallel; for this purpose the wire may be bent at will without doing any harm. When all is so arranged, the magnetic needle will begin to move, so that it turns toward the west under that part of the wire coming from the negative end (pole) of the galvanic apparatus. If the distance between the wire and the needle is not more than 1 1/4 inches, this deflection is about 45°. Beyond this the angle of deflection diminishes as the distance increases. It varies also according to the difference in power of the apparatus.

The connecting wire may be moved toward east or west, so long as it remains parallel to the needle, without other influence on the result, than diminishing the deflection. This action, consequently, is in no wise to be attributed to an attraction; for the same pole of the magnetic needle which turns toward the connecting wire when it is east of the needle, turns away from the same when on the west side of it. This would not be possible if these deflections were due to attraction and repulsion.

(2) The connecting conductor may consist of several wires or metal strips united. The nature of the metal will not alter the effect, unless it be in respect to its amount (Grosse). We used wires of platinum, gold, silver, brass, and iron, as well as strips of tin and lead, and quicksilver with like result. If the conductor is broken by water, this action is not entirely wanting, not even when the stretch of water is several inches long.

(3) The connecting wire acts on the magnetic needle through glass, metal, wood, water, resin, through earthen vessels (topferne Gefasse), and through stone; for when we put a pane of glass, a sheet of metal or a board between the two it did not prevent the effect; indeed all three together seemed scarcely to weaken the influence. Just as little did an electrophorus, a slab of porphyry and an earthen vessel (irdenes Gefass), even when the latter was full of water. Our experiments proved also that the effects mentioned were not altered by using a magnetic needle inclosed in a brass receptacle filled with water. I scarcely need to mention that the passage of these effects through all these substances has never been observed before with electricity or magnetism. The effects produced by (in) the electrical conflict are then wholly different from those of one or another electrical force.

(4) When the connecting wire is in a horizontal plane below the magnetic needle all the specified effects move in an opposite direction to that when it is in a horizontal plane above, but otherwise in precisely similar fashion. The pole of the magnetic needle, below which is that part of the connecting wire into which the electricity came directly from the negative end of the galvanic apparatus, now turns to the east.

This may be more easily remembered by the following formula: The pole above which the negative electricity enters is deflected toward the west; the pole below which it enters, toward the east.

(5) Turning the connecting wire in a horizontal plane so that it gradually makes a larger angle with the magnetic meridian, increases the deflection of the magnetic needle if the turning of the wire be toward the locality of the disturbed needle; it diminishes, however, if the turning be backward from this locality.

(6) A connecting wire in the same horizontal plane as a magnetic needle held in equilibrium (aquilibrirt) by a counter-weight, and parallel with the needle, will not cause it to move either toward east or west, but only to vibrate in the plane of its inclination so that the pole near which the negative electrical force in the wire originates will be depressed if that is to the west of it, or elevated if it is to the east.

(7) If the connecting wire is placed perpendicular to the plane of the magnetic meridian above or below the needle, it remains at rest unless the wire is quite near the pole, in which case the pole will be raised if the current comes from the west side of the wire and depressed if it comes from the east side.

(8) If the connecting wire is placed perpendicularly near one pole of the magnetic needle and opposite it, and the upper end of the wire receives the electricity from the negative end of the galvanic apparatus, this pole moves toward the east; if, on the contrary, the wire is near some point between the pole and the centre of the needle, that will be driven toward the west. When the upper end of the wire receives the electricity from the positive end, precisely the opposite will take place.

(9) If the connecting wire be bent till both parts are parallel, or form two parallel arms, the magnetic pole will be attracted or repelled by it according to circumstances. If the wire be placed opposite one of the two poles of the needle so that the plane of the parallel arms is perpendicular to the magnetic meridian, and the eastern arm be connected with the negative, the western with the positive end of the galvanic apparatus, in this position the nearest pole will be repelled toward east or west, as the position of the plane of the two arms determines. If the eastern arm be connected with the positive, the western with the negative end, the nearest pole will be attracted. If the plane of the arms be brought perpendicular to a point between the pole and the middle of the needle, the same manifestations will be reversed.

(10) A brass needle suspended in the same way as the magnetic needle, will not be moved by the action of the connecting wire. A needle of glass, too, or of gumlac, will remain at rest through all such experiments.

From all this certain conclusions by way of explanation of these phenomena may be deduced. The electrical conflict is able to affect only the magnetic parts of matter. Not all magnetic bodies appear to be permeable to the electric conflict; on the contrary, magnetic bodies, or rather the magnetic portions of them, seem to resist the passage of this conflict, and therefore can be set in motion by the impact of the contending forces.

That the electrical conflict is not confined to the conducting wire, but, as already said, is diffused to some considerable distance through the surrounding space, is sufficiently shown by the observations cited.

From what has been observed we may conclude that this conflict moves in circles; for without this assumption one cannot understand how the same part of the connecting wire, which placed under one pole of the magnetic needle, drives it toward the east, should move it toward the west when placed above it; a circular motion, however, takes place in the opposite ends of a diameter in opposite directions. It appears, furthermore, that this circular movement, in connection with the forward movement lengthwise of the conductor, must describe a helicoid curve or spiral; this, however, if I mistake not, contributes nothing to the explanation of the observed phenomena.

All the effects here given, on the north pole of the needle, are easily understood, if one assumes that the negatively electrical force, or matter, follows a spiral toward the right and repels the north pole, but does not affect the south pole; and just so all effects on the south pole, if one ascribes to the positive electrical force, or matter, a movement in the opposite direction and the ability to act upon the south pole and not the north. Concerning the agreement of this law with nature, further experiments will give more convincing proof than a lengthy explanation; but judgment on the experiments would be much facilitated by diagrams showing the course of the electrical forces in the connecting wire.

I would add to what I have said above that I showed in a work published seven years ago that heat and light are the electrical conflict. From the recent additional observations one may conclude that the motion in circles occurs also in these effects (Wirkungen); this, I believe, may contribute much to the explanation of those facts which we call the polarity of light.

Copenhagen, 21 July, 1820.

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Chicago: Hans Christian Oersted, Experiments as to the Effect of the Electrical Conflict on the Magnetic Needle in The Library of Original Sources, ed. Oliver J. Thatcher (Milwaukee, WI: University Research Extension Co., 1907), 6–10. Original Sources, accessed September 24, 2021, http://originalsources.com/Document.aspx?DocID=D6Y435DYZRZW2EM.

MLA: Oersted, Hans Christian. Experiments as to the Effect of the Electrical Conflict on the Magnetic Needle, in The Library of Original Sources, edited by Oliver J. Thatcher, Vol. 9, Milwaukee, WI, University Research Extension Co., 1907, pp. 6–10. Original Sources. 24 Sep. 2021. originalsources.com/Document.aspx?DocID=D6Y435DYZRZW2EM.

Harvard: Oersted, HC, Experiments as to the Effect of the Electrical Conflict on the Magnetic Needle. cited in 1907, The Library of Original Sources, ed. , University Research Extension Co., Milwaukee, WI, pp.6–10. Original Sources, retrieved 24 September 2021, from http://originalsources.com/Document.aspx?DocID=D6Y435DYZRZW2EM.