456 



ELEMENTS OF ELECTRICAL ENGINEERING. 



go on-ma 



46. The resistances in the various branches of a Wheatstone 

 network are indicated in Fig. 46^. The battery has an electro- 

 motive force of 6 volts in the direction of the arrow. Find 



the current in the galvanometer 

 branch cd and specify its direc- 

 tion. Ans. 0.0001024 ampere 

 from d towards c. 



47. The network shown in 

 Fig. 4.6P has a one-volt voltaic 

 cell of negligible resistance con- 

 nected in the branch db tending 

 to force current from ^/towards b. 

 Find the current in the branch 

 cd and specify its direction. Ans. 0.000735 ampere from c 

 towards d. 



48. A direct-reading ammeter has a resistance of 0.05 ohm, 

 The instrument is provided with a shunt so that the total current 

 passing through the instrument and shunt is 10 times the ammeter 

 reading. What is the resistance of the shunt? Would it be 

 practicable to construct such a shunt, measure its resistance by a 

 Wheatstone' s bridge, and connect it to the ammeter terminals ? 

 If not, how could such a shunt be accurately adjusted? Ans. 

 0.00556 ohm. 



49. The scale of a direct-reading millivoltmeter has 100 divi- 

 sions, each division corresponding to one millivolt between the 

 terminals of the instrument. This instrument is connected to the 

 terminals of a low resistance shunt and each division of the scale 

 corresponds to 0.25 ampere in the shunt. What is the resistance 

 of the shunt? Ans. 0.004 ohrn. 



50. A millivoltmeter has a resistance of 15.4 ohms. What 

 resistance must be connected in series with the instrument so 

 that the scale reading may give volts instead of millivolts ? Ans. 

 15,384.6 ohms. 



51. A direct-reading voltmeter V, Fig. p. 51, having 16,000 

 ohms resistance, is connected from main A to earth. The voltmeter 



