Humboldt State University

Robert A. Paselk Scientific Instrument Museum

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Resistance Box

W. M. Welch Scientific Company

Humboldt S-T-C; c.1926

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Usage/History

This box would be used as a standard resistance in laboratory work in schools. Resistance values are adjusted by removing the brass pegs. The box is constructed with the pegs in parallel with precision wound resistance coils-with the peg in place the current flows through the peg (approx. 0 ohms), when removed the current flows through the resistor.

Some contemporary/early descriptions of the resistance box and its use are provided below:

Description

The instrument is contained in a 8x4x3 3/4h" birch? box stained at one time to look like mahogany. The top is of hard rubber with raised brass-work which has been nickel plated on top, and apparently stained black on the sides. The binding posts are nickel-plated brass with knurled nuts held on by the screw heads. Screws and brasswork are also nickel plated("white") tarnished to black. The resistance value is adjusted by inserting plugs (tapered brass with black hard rubber handles) into holes connecting the brass lugs on the top surface of the case. The total resistance of the box is 1,110 ohms divided as follows: 1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, & 400. The resistance values are all white filled. There is an oval brass tag on the bottom corner of the box beneath the rear binding post stamped: HUMBOLDT S-T-C / 2112. There is a Welch decal in the center of the opposite panel of the box.

 
 

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HSTC (1921-34)
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Last modified 29 August 201