OF ARTS AND SCIENCES. 



139 



current passes through the resistance coils. The current through the 

 coils may be reduced by connecting, through a shunt, the battery- 

 poles which are already connected by the resistance coils, and in this 

 way one can avoid all risk of injuriou.^ly heating tlie fine wire. 



The use of the shunt makes the formula which determines the ratio 

 of the electromotive force of the two batteries a little more complex, 

 but the mechanical work of the comparison is not altered. 



Fig. 2. 



C (Fig. 2) is the strength of the current going through the un- 

 divided circuit. Cp and Cj are the strengtlis of the currents going 

 through the shunt and through the resistance box respectively. Let 

 S be the resistance of the shunt, 



(7= (7,+ Co and C^{R^^R.^= C^.S 



5+ /?! + /?, 



.-. C=Ci 



S 



c. = ^ 



cs 



Kirchoff's Second Law gives, when applied to the closed figures 

 B^, R^, and G, and r, B.^, R.,, and G, 



B, = B,G + 



R,SC 



5 + i^i + i?2 



(1) 



B.,= (r + B.^)G+^^^^^ 



(2) 



