Wednesday, September 26, 2007

Faraday On The Non-Rotation Of Lines-Of-Force

That the metal of the magnet itself might be substituted for the moving cylinder, disc, or wire, seemed an inevitable consequence, and yet one which would exhibit the effects of magneto-electric induction in a striking form. A cylinder magnet had therefore a little hole made in the center of each end to receive a drop of mercury, and was then floated pole upwards in the same metal contained in a narrow jar. One wire from the galvanometer dipped into the mercury of the jar, and the other into the drop contained in the hole at the upper extremity of the axis. The magnet was then revolved by a piece of string passed around it, and the galvanometer-needle immediately indicated a powerful current of electricity. On reversing the order of rotation, the electrical current was reversed. The direction of the electricity was the same as if the copper cylinder or a copper wire had revolved round the fixed magnet in the same direction as that which the magnet itself had followed. Thus a singular independence of the magnetism and the bar in which it resides is rendered evident.


a singular independence of the magnetism and the bar ... is rendered evident: Since a rotating magnet cuts its own magnetic curves, it is “evident” that those curves do not rotate with the magnet to which they belong. The question that was asked in vain for the earth (paragraph 181, comment) is here answered definitively for a small magnet; and it suggests a more fundamental question: What is the relation between a power and the body to which it belongs? That is a question we beg every time we ascribe power to matter: gravity to a body, electricity to a hypothetical fluid—even vital powers to living beings.

Howard J. Fisher

Michael Faraday Wiki Page

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