54 



Art. 9.— T. Terada : 



minimum at x=±h respectively. The end point of tlie vector 

 describes a circle with the radius ijli. 



c) Instead of a linear current, we consider next a current 

 of uniform density 7, with a rectangular section having a breadth 

 of 2/ and a height of 2h, the middle point lying at a height h 

 and the horizontal distance :i- from A. 'Hie two components 

 are respectively given l)y 



i ^ {x^rf+{h-hr ' {x-if+iji+hy 

 "" {x-^if^{h-hf ' (x-iy+(ji-hr 



(h + b)- + x- — I- {h — by + x- — t 



JX=2i'to-^ 



h- + x^—P 



"^ {x-iy + Jr 

 Again, wlicii the current slieet is vertical with a breadtli '2/), 



x- + {h — by 



x- + Jr — b' 



(2) 



,/.io^- C^-+0'-'+( /^+6)'-' (x-ty+jJi-by^ 



"" [x+iy+ih-by {x-iy+{h+by 



.. (x+iy+(h+by {x+iy+ih+by 



^ {x-iy+ih-by ' {x-iy+(h+by 



AVhen the current degenerates into a current sliect of the 

 horizontal breadth 21 and tlie linear intensity i\ 



'2Ih 



•(3) 



•(4) 



In the former case (3), tlie maximum vahie of JZ. J/,, say, 

 which is attained at .f=±V7'+7^', wih increase indefinitely, while 

 the maximum value of JA^, or JX,,, tends to 2-1', when the 

 ratio bjh increases indefinitely. For ^=0. tlie ratio is 1/2. In 

 the latter case (4), JZ,„ varies hom (.) to 4j when 20 increases from 



