PROBLEMS. 455 



the motor being 2,000 feet from the generator, and the electro- 

 motive force between the generator terminals being 125 volts. 

 Ans. 230,000 circular mils. 



43, A motor receiving 100 kilowatts of power is at a distance 

 of 1 5 miles from the generator. Line wires 200 mils in diameter 

 are to be used. The line loss is to be 10 per cent, of the gen- 

 erator output. Find : (a) the current ; () the voltage at the 

 generator; and (c) the voltage at the motor. Ans. (a) 16.12 

 amperes; (b) 6,894 volts; (c) 6,204 volts. 



NOTE. High voltage direct current power transmission is not used in American 

 practice. 



44. Six cells of battery each having an electromotive force (on 

 open circuit) of 2. 1 volts and a resistance of 5 ohms are connected 

 as shown in Fig. 44/1 The resistance of ab is 150 ohms, (a) 

 Locate the point P so that no current will be indicated by the 

 galvanometer G. (&) The con- 

 tact P being "at the middle point \^r-\l 1 1 1 1 1 1 I 



of ab and the total resistance of 

 the path MGP being 25 ohms 

 find: (i) the current in each 

 path a, b and G t and (2) the 



MSK 



PL 



electromotive force between the I5 ohm3 



terminals of the left-hand cell 



and the voltage between M and N. Ans. (a) ajb = o.2\ (b) 



0.042 ampere in a, 0.0924 ampere in b, 0.0504 ampere in G ; 



1.89 volts between terminals of left-hand cell, and 8.19 volts 



between M and N. 



45. A one-ohm coil is tested and found to have a resistance of 

 1.004 ohm. (a) What length of German silver wire having a 

 resistance of I 5 ohms per meter must be connected in parallel 

 between the terminals of the coil to give a combined resistance of 

 i ohm ? (b) Suppose that an error of 5 per cent, is made in 

 measuring off the required length of the German silver ; what 

 will be the percentage error of the corrected one-ohm coil ? Ans. 

 (a) 16.73 meters ; (b) about T 2 ^ of one per cent. 



