RESISTANCE DEVICES 



139 



The path of the current is down the outside strip from e to d, 

 across the copper connection strip k, then up from a to b and 

 down to c across k to g and up to the terminal b. The potential 

 leads are attached at e and /. Mica insulation is used between 

 the leaves of resistance material. 



TABLE 



OF DATA CONCERNING OIL-COOLED MANQANIN RESISTANCES 

 REICHSANSTALT DESIGN WITH LEAVES 0. 5 MM. APART 



The effects of the self-induction of a shunt intended for use 

 in potentiometer methods may be compensated by mutual 

 induction between the shunt and the potential leads. 



a 6 



R.L 



.. 

 FIG. 03. Compensation for shunt inductance. 



Referring to Fig. 63, at balance no current flows in the voltage 

 leads to a and b. It is desired to make the potential difference 

 between the terminals a and b equal to and in phase with the 

 ohmic drop in R. The potential difference between c and d is 

 shown in the vector diagram by V C d- If the potential leads are 

 arranged so that there is mutual induction between them and 

 the main part of the shunt, the e.m.f. induced in the potential 

 circuit will be proportional to and in quadrature with the current 

 7 through the shunt. 



The mutual inductance, m, may be arranged so that its action 

 either aids or opposes the reactive drop in the shunt. If it op- 

 poses, then the P.D. between a and b is given on the vector dia- 

 gram by Vab, and if the mutual inductance be adjusted so that 



