AN ELEMENTARY TREATISE 



ON 



ALTERNATING CURRENTS 



CHAPTER I. 



Introductory Law of Force Unit Pole Strength of Magnetic Field Unit 

 Current Magnetic Field due to Solenoid Distinction between Induction 

 and Magnetizing Force Magnetic Field due to an Electric Current Self 

 and Mutual Induction Potential Specific Inductive Capacity Equt- 

 potential Surfaces Capacity Condensers Energy of a charged Condenser. 



INTRODUCTORY. 



1. Magnetic Force. If a magnet is placed anywhere in 

 space and a pivoted magnet or compass needle is placed near it, 

 the latter always takes up a definite position relative to the former. 

 The magnet exerts a force on each end of the compass needle, 

 which has a definite direction at every point at which the needle 

 is placed, and the magnitude of the force is the same as if two 

 equal quantities, -f- in and m, of magnetism (whatever magnetism 

 may be), but of opposite sign, were situated at definite points 

 within the magnet. These two points are called the poles of the 

 magnet, and m is called the Pole Strength. 



If we could isolate one of the poles of the compass needle we 

 should find that at every point in space it would be urged in a 

 definite direction, due to the action of the magnet, and if it were 

 always moved in the direction in which the magnet urged it, 

 a definite curve would be traced, the tangent at every point of 

 which would give the direction of the force at that point. 



B 



