apparatus for showing induction of the earth
Date: 1848-1855
Inventory Number: 0105
Classification: Induction Coil
Attributed to: Daniel Davis, Jr. (1813 - 1887)
Cultural Region:
Place of Origin:
Dimensions:
28 × 29.5 × 14.5 cm (11 × 11 5/8 × 5 11/16 in.)
Bibliography:
Davis's 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
A Manual of Magnetism
Daniel Davis, Jr. and the Elecromagnetic Instrument Industry: A Field with Great Potential in the Early 19th Century
Description:
A three-layer simple winding helical wire coil, insulated in green-painted thread, is held in a brass holder revolving in the vertical plane. A crank handle (handle missing) and gearing, fixed on one of the two turned supporting brass columns, allows this coil to be spun rapidly and easily. The coil's wire ends make contact (at a revolving pole changer) to two copper wires which terminate in the brass binding posts found at one end of the base. The latter, rectangular in shape, is supported by four brass ball feet.
The instrument has two old Harvard numbers: "7-64" and "6-3-7".
The device was sold $12.00 by Davis in 1848.
The instrument has two old Harvard numbers: "7-64" and "6-3-7".
The device was sold $12.00 by Davis in 1848.
Signedunsigned
FunctionFor instructional demonstration of the induction of electricity in coiled wires when the coil is rapidly turned in the presence of Earth's magnetism.
This is how Davis described the experiment in 1848: "Stronger deflections are produced by causing a helix [coil] to revolve rapidly, as in the instrument represented in Fig. 184. The coil which is hollow, moves in a vertical plane, and its shaft is provided with a pole-changer, to the segments of which the extremities of the wire are soldered. The springs pressing on these segments convey the currents to the screw-cups on the base board. When the cups are connected with those of a delicate galvanometer, and the instrument placed in such a direction that the helix shall move in the magnetic meridian, it is made to revolve rapidly by means of a multiplying wheel. As each end of the helix approaches and recedes from the line of the dip, opposite currents are induced in the wire, their direction changing as the helix passes this point." (pp. 306-307)
This is how Davis described the experiment in 1848: "Stronger deflections are produced by causing a helix [coil] to revolve rapidly, as in the instrument represented in Fig. 184. The coil which is hollow, moves in a vertical plane, and its shaft is provided with a pole-changer, to the segments of which the extremities of the wire are soldered. The springs pressing on these segments convey the currents to the screw-cups on the base board. When the cups are connected with those of a delicate galvanometer, and the instrument placed in such a direction that the helix shall move in the magnetic meridian, it is made to revolve rapidly by means of a multiplying wheel. As each end of the helix approaches and recedes from the line of the dip, opposite currents are induced in the wire, their direction changing as the helix passes this point." (pp. 306-307)
Curatorial RemarksSee Michael Faraday's Series 1 and 2 Experimental Researches on Electricity (1831-1832) for early origins of this effect.
The pole changer, devised by Charles Grafton Page, is a feature of many of Davis's instruments. In this one it is particularly visible and well worked out. Notice how the electrical contacts are made between the rapidly rotating coil and the pole changer.
A similar instrument, though not identical (brass holders and crank and handle not included) is found in the 1842 version of Davis's book on magnetism.
The pole changer, devised by Charles Grafton Page, is a feature of many of Davis's instruments. In this one it is particularly visible and well worked out. Notice how the electrical contacts are made between the rapidly rotating coil and the pole changer.
A similar instrument, though not identical (brass holders and crank and handle not included) is found in the 1842 version of Davis's book on magnetism.
Primary SourcesDaniel Davis, Jr., Catalogue of Apparatus, to Illustrate Magnetism, Galvanism, Electrodynamics, Electro-Magnetism, Magneto-Electricity, and Thermo-Electricity (Boston: Daniel Davis, Jr., 1848), 39, fig. 184.
Daniel Davis, Jr., A Manual of Magnetism, 2nd ed. (Boston: Daniel Davis, Jr., 1848), 306-308.
Daniel Davis, Jr., Davis's Manual of Magnetism, 7th ed. (Boston: Palmer and Hall, 1855), 306-308.
Daniel Davis, Jr., A Manual of Magnetism, 2nd ed. (Boston: Daniel Davis, Jr., 1848), 306-308.
Daniel Davis, Jr., Davis's Manual of Magnetism, 7th ed. (Boston: Palmer and Hall, 1855), 306-308.
ProvenanceFrom the Department of Physics, Harvard University.