Immagini

DESCRIPTION

Exhibit 692 is an instrument designed around 1837 by P. T. Riess (1805-1885) to demonstrate and measure the thermal effects of the passage of current in a conducting wire.

The apparatus consists of a glass tube bent twice at 90°: on one end there is a small funnel and on the other a glass globe containing a spiral of conducting wire with external terminals. This tube is mounted on an adjustable inclined plane (see design-1). To perform the experiment one pours some sulfuric acid mixed with alchohol in the funnel that rises to a certain level according to the set inclination. When one discharges a condenser through the spiral, the heat causes the air in the globe to expand and move the meniscus of the liquid. Riess determined that the heat generated in the wire was proportional to the square of the charge transferred.

BIBLIOGRAPHY

• [1] Riess, Pogg. Ann. 48, 335, 1837; 49, 49, 1838.

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