. Bulletin of the scientific laboratories of Denison University. Thermo-electric Couples 251 was connected in series with the galvanometer and thermo- couple, and by means of this resistance, suitable sensitiveness was obtained. Standardization of galvanometer (fig. 7). In order to be able to determine electromotive force by means of a galvanometer it was standardized by the "fall of potential" method, as follows:— A primary circuit was made up of (1) a source of electromotive force (dry cell), (2) an adjustable resistance, r (3) a milliammeter. (4) a known resistance, R, such as a b
. Bulletin of the scientific laboratories of Denison University. Thermo-electric Couples 251 was connected in series with the galvanometer and thermo- couple, and by means of this resistance, suitable sensitiveness was obtained. Standardization of galvanometer (fig. 7). In order to be able to determine electromotive force by means of a galvanometer it was standardized by the "fall of potential" method, as follows:— A primary circuit was made up of (1) a source of electromotive force (dry cell), (2) an adjustable resistance, r (3) a milliammeter. (4) a known resistance, R, such as a bridge wire, or standard ohm. The terminals of the galvanometer circuit including the "ad- justing resistance" S were connected across R; then for a given current / flowing around the primary circuit, the electromotive force acting on the galvanometer circuit is equal to Fig. 7. Arrangement for standardizing galvanometer. By adjusting r various values of / are obtained, hence various electromotive forces. Results were recorded as follows: (a) (b) (c) (d) Amperes (M'A) Deflection (G) EMF [{ai)xR] Volts per mm. [(c)/(b)] (a) and (b) are obtained from readings of instruments MA and G; (c) is obtained by multiplying (a) by the resistance R; and (d) is found by dividing (c) and (b). Example: Re- sistance R = .444 ohm. (a) ,00268 (b) 25mm. (c) .001189 (d) ,0000476 Now, the electromotive force of any thermo-couple acting is at once obtained by multiplying the deflection of the galvanome- ter by the factor (d).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Denison University; Denison Scientific Association. Granville, Ohio : [The University]
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