60 ELEMENTS OF ELECTRICITY AND MAGNETISM. 



with a battery of three volts electromotive force and negligible 

 resistance. What is the current in the 2-ohm and 3-ohm resist- 

 ances ? Ans. 0.5 ampere, 0.66 ampere. 



56. Six voltaic cells, each having a resistance of 2 ohms, are 

 connected to a coil of which the resistance is 5 ohms. What is 

 the total resistance of the circuit : (a) When the 6 cells are con- 

 nected in series, () when the 6 cells are connected 2 in parallel 

 by 3 in series ; (<:) when the 6 cells are connected 3 in parallel 

 by 2 in series ; and (d) when the 6 cells are connected in paral- 

 lel ? Ans. (a) 17 ohms, (b] 8 ohms, (c] 6^ ohms, and (d) 5^ 

 ohms. 



The electromotive force of each cell is 1 .6 volts. What current 

 is produced in the coil in each of the above cases ? Ans. (#) 0.57 

 ampere, (<) 0.6 ampere, (^)o.5 ampere, (</) 0.3 ampere. 



Note. When n voltaic cells are connected in series, their combined electromotive 

 force is nE, where E is the electromotive force of one cell. 



57. 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. 



58. A milli voltmeter 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. 



"^ 59. The scale of a direct-reading milli voltmeter has 100 divis- 

 ions, 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 ohm. 



