CHAPTER IV 
THE PHYSICAL PRINCIPLES UNDERLYING THE MEASURE- 
MENT OF BREAK SHOCKS 
HELMHOLTZ* appears to have been the first to study 
in detail break induction shocks. He established the 
principles which are still accepted as to their formation 
and course. His work was chiefly from the physical 
standpoint, although he gave attention also to the physi- 
ological aspect of the problem. More recently Fleming f 
has given a clear and concise discussion of break incluc- 
tion shocks, his presentation agreeing in every essential 
particular with the earlier one of Helmholtz. The fol- 
lowing statement is, in the main, condensed from Flem- 
ing's discussion. 
The Course of Break Induced Currents. The current 
induced in a secondary coil by the breaking of the 
primary current may be represented graphically by such 
a curve as is given in Fig. 10, beginning at zero, increas- 
ing rapidly to a maximum, and then falling more slowly 
away to zero. If the break of the primary were abso- 
* Helmholtz: Poggendorf's Annalen der Physik und Chemie, 1851, 
Ixxxiii, S. 536. Also, Ges. Abh., S. 459. 
t Fleming: The Alternate Current Transformer, London, 1892, i, 
pp. 184 et seq. 
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