Page:A Treatise on Electricity and Magnetism - Volume 1.djvu/455

358.] strength of current, so as to determine how the strength of current effects the resistance.

If $$y$$ is the current in the galvanometer, the actual current through the battery is $$x_0$$ with the key down and $$x_1$$ with the key up, where the resistance of the battery is and the electromotive force of the battery is

The method of Art. 356 for finding the resistance of the galvanometer differs from this only in making and breaking contact between $$O$$ and $$A$$ instead of between $$O$$ and $$B$$, and by exchanging $$\alpha$$ and $$\beta$$ we obtain for this case

On the Comparison of Electromotive Forces.

358.] The following method of comparing the electromotive forces of voltaic and thermoelectric arrangements, when no current passes through them, requires only a set of resistance coils and a constant battery.

Let the electromotive force $$E$$ of the battery be greater than that of either of the electromotors to be compared, then, if a sufficient resistance, $$R_1$$, be interposed between the points $$A_1,\, B_1$$ of the primary circuit $$EB_1A_1E$$, the electromotive force from $$B_1$$ to $$A_1$$