ELECTRON THEORY 



By R. G. Kloeffler 

 Fellow of the American Institute of Electrical Engineers 



The discovery of the electron dates back to the beginning of the 

 present century. This important event was foreshadowed by many 

 early experiments and theories. In 1725, DuFay discovered that the 

 gaseous region around a red-hot body would conduct electricity. In 

 1879, Crookes found that the rays in his experimental tubes were 

 negatively charged particles. Edison's experiments with the incan- 

 descent lamp led to the discovery in 1883 that an electric current did 

 flow from an incandescent filament to a plate in a vacuum but that 

 it would flow in only one direction. This is known as the Edison 

 effect. J. J. Thomson is generally given credit for the discovery of 

 the electron because of his experiments and reports to the scientific 

 world in a period shortly before and after the year 1900. He devel- 

 oped a very ingenious method for measuring the charge on the ion 

 and secured an approximate value of the magnitude of that charge. 

 Wilson and other scientists made some improvements on Thomson's 

 method and secured other approximate values for the magnitude of 

 the charge of the electron. It remained for an American physicist, 

 Robert Millikan, to make further refinements in the method of meas- 

 uring the magnitude of the charge and thereby secure results an- 

 nounced to the world in 1913 which were absolutely convincing as to 

 the existence of and the value of that fundamental electrical charge 

 on the electron. This electron was a minute indivisible negative 

 charge of electricity having a very small mass. The term "electron" 

 has always been associated with the negative charge while the term 

 "positive electron" has been associated with another complimentary 

 unit, the proton. 



Four years ago a cosmic-ray photograph taken at the Norman 

 Bridge Laboratory showed unmistakable evidence of the track of a 

 particle having the same mass and the same magnitude as the charge 

 on the electron but of the opposite sign. Thus was discovered the 

 true positive electron, or what is often termed the positron. This 

 recent discovery of the positron has raised many questions in the 

 scientific mind and has tended to upset some of our well-accepted 

 theories regarding matter. 



1 Reprinted by permission from Electrical Engineering, vol. 67, No. 1, January 1938. 



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