A laboratory guide in physiology / by Winfield S. Hall ; with appendices on organization and equipment.

  • Hall, Winfield Scott, 1861-1942.
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: A laboratory guide in physiology / by Winfield S. Hall ; with appendices on organization and equipment. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    plate uncoupled. These two uncoupled terminal plates of the battery are the ones from which to lead off the wires to the other apparatus, which should be arranged as shown in PI. I., Fig. 6. Repeat the observations on the angle of deviation of the needle, using the 0£1, lOfl and 100.fi resistance as above. I 6) Join up four cells tandem or in series, and repeat the three observations. (7) Join up six cells in series and repeat observations. (8) Tabulate results and draw conclusions. 1. There is a marked difference in the results of the two methods. 2. With low external or circuit resistance the current as indicated by the angle at which the detector needle stood increased with an increase in the number of cells joined in multiple arc or abreast. 3. With high external resistance the strength of the current does not seem to be essentially increased by in- creasing the number of cells joined up abreast. 4. With low external resistance the strength of the current is not increased by adding cells in series. 5. With high external resistance the strength of current increases with an increase in the number of cells joined up in series or tandem. The following theoretical points are worthy of note : The general formula C = g does not differentiate le tween that part of the resistance furnished by the battery and that part furnished by the external circuit. The former is called internal resistance (ri) and the latter is called external resistance (re). So we may write R = ri + re and C =~— 1 ri+re •