rectangle electromagnet revolving on its axis
Date: 1848-1855
Inventory Number: 0112
Classification: Electromagnet
Attributed to: Daniel Davis, Jr. (1813 - 1887)
Cultural Region:
Place of Origin:
Dimensions:
23.2 × 19 × 8.5 cm (9 1/8 × 7 1/2 × 3 3/8 in.)
Bibliography:
Davis's Manual of Magnetism
A Manual of Magnetism
Catalogue of apparatus to illustrate magnetism, galvanism, electrodynamics, electromagnetism, magneto-electricity, and thermo-electricity, manufactured and sold by Daniel Davis, magnetical instrument maker
Daniel Davis, Jr. and the Elecromagnetic Instrument Industry: A Field with Great Potential in the Early 19th Century
Description:
A turned brass column supports a three-layer rectangular coil. Inside it, a smaller three-layer coil rotates on a pivot. The windings are painted green on both coils. The revolving coil is linked to a pole changer device. The instrument is supported by a mahogany base on four brass ball feet. Two binding posts were linked to a battery, providing electricity to the outer coil.
The instrument is tagged with an old Harvard number: "6-3-16".
It was sold $7 by Davis in 1848.
The instrument is tagged with an old Harvard number: "6-3-16".
It was sold $7 by Davis in 1848.
Signedunsigned
FunctionDemonstration apparatus that shows how electromagnetic rotation occurs when current passes through coils. The rectangular coils in the middle rotate, and by rotating invert the polarity of the outside coil by a pole changer. It is this repeated pole inversion that powers the system.
Here is how Davis described this instrument in 1848: "Rectangular coils may be used in place of circular ones, with the same result, as in the instrument represented in Fig. 163... The inner rectangle revolves in the same manner as the coil B in the instrument last described, and the rotation is more rapid than with the circular coil. In consequence of the width of the rectangular coils being less than their height, the sides of the interior one are near those of the other during the whole revolution. This circumstance is the occasion of its greater speed."
Here is how Davis described this instrument in 1848: "Rectangular coils may be used in place of circular ones, with the same result, as in the instrument represented in Fig. 163... The inner rectangle revolves in the same manner as the coil B in the instrument last described, and the rotation is more rapid than with the circular coil. In consequence of the width of the rectangular coils being less than their height, the sides of the interior one are near those of the other during the whole revolution. This circumstance is the occasion of its greater speed."
Primary SourcesDaniel Davis, Jr., Catalogue of Apparatus, to Illustrate Magnetism, Galvanism, Electrodynamics, Electro-Magnetism, Magneto-Electricity, and Thermo-Electricity (Boston: Daniel Davis, Jr., 1848), 13, fig. 163.
Daniel Davis, Jr., A Manual of Magnetism, 2nd ed. (Boston: Daniel Davis, Jr., 1848), 237.
Daniel Davis, Jr., Davis's Manual of Magnetism, 7th ed. (Boston: Palmer and Hall, 1855), 237.
Daniel Davis, Jr., A Manual of Magnetism, 2nd ed. (Boston: Daniel Davis, Jr., 1848), 237.
Daniel Davis, Jr., Davis's Manual of Magnetism, 7th ed. (Boston: Palmer and Hall, 1855), 237.
ProvenanceFrom the Department of Physics, Harvard University.