Michael Faraday, his life and work / by Silvanus P. Thompson.

  • Silvanus P. Thompson
Date:
1901
Catalogue details

Licence: In copyright

Credit: Michael Faraday, his life and work / by Silvanus P. Thompson. Source: Wellcome Collection.

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    an gins to tlie line of tlie current, the sense of the deviation depending upon the direction of flow of the current, and also on the position of the wire as to whether it were above or below the needle. A current flowing from south to north over the needle caused the north-pointing end of the needle to be deflected westwards. If the wire were vertical, so that the current flowed downwards, and a compass needle was brought near the wire on the south side, therefore tending under the earth’s directive influence to point northwards toward the wire, it was observed that the effect of the current flowing in the wire was to cause the north-pointing end of the needle to turn west- wards. Or, reversing the flow of current, the effect on the needle was reversed ; it now tended eastwards. All these things Oersted summed up in the phrase that “ the electric conflict acts in a revolving manner ” around the wire.* In modern phraseology the whole of the actions are explained if one can conceive that the effect of the electric flow in the wire is to tend to make the north pole of a magnet revolve in one sense around the wire, whilst it also tends to make the south pole of the magnet revolve around the wire in the other sense. The nett result in most cases is that * “ To the effect which takes place in this conductor [or uniting wire] and in the surrounding space, we shall give the name of the conjlict of electricity.” .... “From the preceding facts we may likewise collect that this con- flict performs circles ; for without this condition, it seems impossible that the one part of the uniting wire, when placed below the magnetic pole, should drive it towards the east, and when placed above it towards the west; for it is the nature of a circle that the motions in opposite parts should have an opposite direction.”—H. G. Oersted, Ann. of Phil., Oct. 1820, pp. 273 -276.
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