D 



An Investigation into the Nature of the Field of the 



Positive Charge, and the Direction of Flow 



of the Electric Current. 



By H. LaY. Twining, Professor of Physics and Electrical En- 

 gineering, Los Angeles Polytechnic High School. 



HISTORY. 



N 1879 Crookes showed that the cathode ray is a stream 



of negatively charged particles, by causing them to be 



deflected in an electromagnetic field. 



In 1893 Lenard showed that the cathode ray could pene- 

 trate an aluminum window through which the atoms could 

 not pass. They were thus shown to be smaller than the atom ; 

 i. e. the particles that constitute the cathode ray, are smaller 

 than the atoms of the gas contained in the vacuum tube. 



In 1896 Perrin of France showed that the cathode ray 

 imparts negative charges to objects upon which it falls. 



In 1897 Lenard and J. J. Thomson definitely showed that 

 the mass of the cathode ray particle is 1-1830 the mass of the 

 hydrogen atom. The cathode ray is also deflected by an electro- 

 static field. 



Millikan, at the Chicago University, recently measured by 

 a unique and accurate method single negative and positive 

 charges and combinations of these charges up to 200 by actual 

 count and found their values in close agreement with those 

 found by others. 



In the light of the above results, and also in the light of 

 many other experiments, it has been concluded that the elec- 

 tric current that flows in a metallic conductor consists of a 

 stream of negative charges. The negatively charged particle 

 is called an electron, and it moves at various speeds, depend- 

 ing upon the conditions under which it is placed. In Crooke's 

 tubes it has been found to approach the speed of light, but 

 never has been known to reach it. At one half the speed of 

 light, the electron sensibly increases its mass and when it dif- 

 fers from the velocity of light in the ratio of 1 :99999 it has 

 ten times the mass that it has at one half the speed of light. 

 No positive charge has been found flowing in a metallic con- 

 ductor. Both negative and positive charges are found asso- 

 ciated with the atoms in an electrolyte, and when so associ- 

 ated their speed is very slow, being of the order of a few 

 centimeters per hour. In this case they flow in opposite direc- 

 tions. But this flow of ions in an electrolyte does not consti- 

 tute an electric current, because Hopkins has shown that the 

 speed of the electric current is the same in a metallic conductor 

 and an electrolyte, provided the ohmic resistance of both is 

 the same. A very slight experience with electricity also clearly 



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