Immagini

DESCRIPTION

Exhibit 168 is a Kohlrausch bridge that works like a Wheatstone bridge but is designed for measuring resistances of liquids in a cell or also solids. It is powered by a spark coil at about 1000 Hz to avoid electrolytic polarization at the electrodes and the balanced condition is revealed by zero sound in a set of earphones. The balance point is found by moving a cursor along a graduated platinum wire along which is distributed the entire potential difference of the spark coil.

IF (J in fig. 3) is the balance point, that is minimum sound:

where X is the resistance of the liquid;
L1 is the distance E - J;
L2 is the distance J - F;

ISCRIZIONI

1. Sulla base di legno è inciso il nome del costruttore "Hartmann & Braun - Frankfurt A/M"
2. Numero inciso sotto il nome del costruttore: 668
3. Scritta sotto la base di legno: 400/150

BIBLIOGRAPHY

• [1] L. Graetz, "L'Elettricità e le sue Applicazioni", pag.90

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