Rechercher dans les textes édités
Histoire de l'électricité > OERSTED, Experiments on the Effect of a Current of Electricity on the Magnetic Needle, 1820.
|<       <      Page 275      >      >|
Aller à la page
Even glass, metal, and wood, interposed at once, do not destroy, and indeed scarcely diminish the 
effect. The disc of the electrophorus, plates of porphyry, a stoneware vessel, even filled with 
water, were interposed with the same result. We found the effects unchanged when the needle was 
included in a brass box filled with water. It is needless to observe that the transmission of 
effects through all these matters has never before been observed in electricity and galvanism. The 
effects, therefore, which take place in the conflict of electricity are very different from the 
effects of either of the electricities. 
If the uniting wire be placed in a horizontal plane under the magnetic needle, all the effects are 
the same as when it is above the needle, only they are in an opposite direction ; for the pole of 
the magnetic needle next the negative end of the battery declines to the east. 

That these facts may be the more easily retained, we may use this formula––the pole 
above which the negative electricity enters is turned to the west; under which, 
to the east. 

If the uniting wire is so turned in a horizontal plane as to form a gradually increasing angle with 
the magnetic meridian, the declination of the needle increases, if the motion of the wire is 
towards the place of the disturbed needle ; but it diminishes if the wire moves further from 
that place. 
When the uniting wire is situated in the same horizontal plane in which the needle moves by means 
of the counterpoise, and parallel to it, no declination is produced either to the east or west ; but 
an inclination takes place, so that the pole, next which the negative electricity enters the 
wire, is depressed when the wire is situated on the west side, and elevated when 
situated on the east side. 

If the uniting wire be placed perpendicularly to the plane of the magnetic meridian, whether above 
or below it, the needle remains at rest, unless it be very near the pole ; in that case the pole is 
elevated when the entrance is from the west side of the wire, and depressed, 
when from the east side. 

When the uniting wire is placed perpendicularly opposite to the pole of the magnetic needle, and 
the upper extremity of the wire receives the negative electricity, the pole is moved towards the 
east ; but when the wire is opposite to a point between the pole and the middle of the needle, the 
pole is moved towards the west. When the upper end of the wire receives positive electricity, the 
phenomena are reversed.  

If the uniting wire is bent so as to form two legs parallel to each other, it repels or attracts 
the magnetic poles according to the different conditions of the case. Suppose the wire placed 
opposite to either pole of the needle, so that the plane of the parallel legs is perpendicular to 
the magnetic meridian, and let the eastern leg be united with the negative end, the western leg with 
the positive end of the battery: in that case the nearest 
|<       <      Page 275      >      >|
Aller à la page
Télecharger le PDF en format texte ->Créer son extrait avec MonPDF Marquer cette page avec votre compte ICEberg+

© CRHST/CNRS, 2005 / Développé sous ICEberg 4.0.2 / hébergement CC-IN2P3 / Directeur de publication : Christine Blondel, responsable informatique : Stéphane Pouyllau