520 



SUBMAKINE CABLE LAYING AND REPAIRING. 



to E — e (or d in the Muirhead test). By putting these values 

 in the previous formula the battery resistance becomes 



&=r£ ohms, 

 where E is, as before, the resistance of the battery shunt. 



Mance's Battery Resistance Test. — In Mance's battery re- 

 sistance test by bridge the battery is connected through the 



Shunt 



nmow) 



Hi|i|i|i|i|i|i|h 



, Fig. 290. — Mance's Battery Resistance Test. 



usual battery key to the line and earth terminals (Fig. 290). 

 Balance is obtained when no change in the galvanometer de- 

 flection occurs on opening or closing the test key. The resistance 

 of the battery is then found by the ordinary bridge proportion, 

 as if it was a simple resistance without E.M.F. It is necessary 

 to use a shunt on the galvanometer to bring the deflection 

 conveniently within the scale, and it is sometimes convenient, 

 when the battery is a small one, to add a resistance to it, which 

 is afterwards deducted from the bridge result. 



