PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 



137 



zinc ; this was fastened down on a table over a number of sheets of co- 

 ordinate paper, and the value of A was determined by measuring on the 

 paper the position of a straight edge which touched the template at 

 any desired point. 



TABLE II. 



If after the core of Q had been demagnetized, a steady electromotive 

 force of E volts were applied to the exciting circuit of resistance 

 ?• ohms, containing the coil of 1394 turns, and if eddy currents were 

 nonexistent so that the core followed the statical magnetizing curve, 

 the march of the current (in amperes) would be given by the equation 



E -ri= 13.94.x- 



di 

 dt' 



(18) 



whence 



r 13.94 A ,. 

 Jr. E — ri 



(19) 



If from an actual current curve obtained from Q for a given journey 

 of the core we were to determine the corresponding magnetizing curve 

 for the metal (flux versus coil current), we should find that the values 

 of the flux, for small values of the current, at least, would fall short of 

 the flux values which the same currents would cause if they were to act 



