Images(3)

earth inductor with stand

Date1893-1912

Inventory Number1997-1-0670

ClassificationInductance

Subject

Maker Elliott Brothers 1853 - 1916

Maker Queen & Company ? 1893 - 1912

Supplier Queen & Company ? 1893 - 1912

Cultural Region

Place of Origin

Dimensions50.5 × 48.4 × 40 cm (19 7/8 × 19 1/16 × 15 3/4 in.)

Material

DescriptionCircular flip coil hinged to rotate inside a square wooden frame. The square frame itself is mounted on vertical arms so it can be turned on a horizontal axis. The square frame has two binding posts that connect via brass contacts to the coil. On the opposite side to the binding posts there is a crank with a wooden handle to turn the coil inside the square frame.

On the end of one of the axles supporting the square frame is a circular brass scale marked in degrees, 0-90 in four quadrants, with 0 on top and bottom marking the vertical position, and 90 twice marking the horizontal position. The pointer is two-sided, pointing to the same value at opposite ends of the circle.

Signedon brass knob on side of instrument: ELLIOTT BROS. / LONDONAC on base JAMES W. QUEEN & Co. PHILADA

Inscribedon base in white paint MA10 numbers inscribed: 7-59 [?]

Curatorial RemarksThe wooden handle of the crank is loose, stored tied to the coil. The brass scale is loose and currently misaligned with respect to the wooden frame. see 1997-1-0643 and 1997-1-0668.

FunctionFrom the website of the physics department at Kenyon College available here:

"The Earth Inductor is a flip coil used to measure the magnitude and direction of the earth's magnetic field. The rotating coil is quickly flipped through 180 degrees, and the output is fed to a ballistic galvanometer. This device, with a long period of oscillation, measures the total charge delivered by the induced EMF; the charge is then proportional to the magnitude of the magnetic field threading the coil.

The experiment is done with the coil horizontal (to find the vertical component of the earth's field) and vertical (to find the horizontal component). The direction and net field can then be readily calculated."