49 8 ELEMENTS OF ELECTRICAL ENGINEERING. 



184. A slim rod 25 centimeters long is made into a link which 

 passes through a coil of 50 turns of wire in which a current of 1 5 

 amperes is flowing. Find the average value along the rod of the 

 component parallel to the rod of the magnetic field due to the 

 coil. Express the result in gausses. Ans. 37.7 gausses. 



185. Reduce a field intensity of 25 ampere-turns per inch to 

 gausses. Ans. 12.37 gausses. 



186. Show by dotted lines the various magnetic circuits in 

 Figs. 32 to 39 of Chap. II. Let of represent the magnetomo- 

 tive force of a single field coil in each figure. What is the mag- 

 netomotive force acting on each magnetic circuit? Ans. 2& in 

 Fig. 32 ; 2c?in Fig. 33 ; e^in Fig. 34; & 'in Fig. 35 ; 2c^in Fig. 

 36; 2cMn Fig. 37; cf'm Fig. 38; and 2cMn Fig. 39. 



187. An iron rod 2x2 centimeters square and 20 centimeters 

 long is magnetized to an intensity of 1,000 units pole per square 

 centimeter section when it is placed in a region which, but for the 

 action of the poles of the rod, would be a uniform field parallel 

 to the rod and of an intensity of 102 gausses. Assuming the 

 poles of the rod to be concentrated at its ends calculate the net 

 magnetizing field at the center of the rod. Ans. 22 gausses. 



188. Find the total magnetic flux through the middle part of 

 the iron rod specified in problem 187. Ans. 50,353.6 maxwells 

 or lines. 



Note. One part of the flux is ^irm and the other part is cHs, where eft is the 

 net magnetizing field at the middle of the rod. 



189. A bar magnet of hard steel is 2 x 2 centimeters square 

 and 20 centimeters long, and the strength of each pole of the 

 magnet is 2,000 units. The magnet is placed in a region which, 

 but for the presence of the magnet, would not be a magnetic 

 field. Find the total magnetic flux through the middle part of 

 the magnet. Ans. 24,972.8 maxwells. 



Note. In this case the net magnetizing force, <$ at the middle of the bar is a 

 demagnetizing force, and the flux due to &C is subtracted from ^irm. 



190. A transformer has a sheet iron core of which the uniform 

 sectional area is 120 square centimeters. The mean length of 



