9 o 



ELEMENTS OF ELECTRICITY AND MAGNETISM. 



north pole of 600 units strength at Washington. Ans. 1.07 

 gausses^ north, and dipping at tan" 1 0.5452 (2836') below the 

 horizontal. 



68. Find the distance and direction from the magnet pole 

 specified in problem 67 to the point at which the resultant field 

 is zero. Ans. 32.16 centimeters, south, and elevated 62 above 

 the horizontal. 



69. A room 6 meters long by 5 meters wide by 3 meters high 

 has its longest dimension magnetic north and south. The inten- 

 sity of the earth's field in the room is 0.62 gauss and the dip is 

 72. Find the number of lines of magnetic flux across each of 

 the walls, the ceiling, and floor of the room and specify in each 

 case whether the flux is passing out of the room or into the room. 

 Ans. East wall, o ; west wall, o ; north wall, 28,740 maxwells 

 out; south wall, 28,740 maxwells in; ceiling, 176,900 maxwells 

 in; floor, 176,900 maxwells out. 



70. The pole face of the field magnet of a dynamo has an area 

 2O centimeters by 30 centimeters. The magnetic field between 

 the pole faces and the armature core is perpendicular to the pole 

 face at each point and its intensity is 6,000 gausses. Calculate 

 the number of lines of force which pass from the pole face into 

 the armature core. Ans. 3,600,000 maxwells. 



71. Calculate the number of lines of force which emanate from 

 the north pole of one of the magnets specified in problem 60. 

 Ans. 4,400 maxwells. 



cm, \ 



N 



N N 



s 



S -S 



tnd view 



nidc view 



Fig. 56. 



