20 



ADVANCED ELECTRICITY AND MAGNETISM. 



abampere, the c.g.s. unit of resistance the abohm, the c.g.s. unit 

 of electromotive force the abvolt, the c.g.s. unit of capacity the 

 abfarad, and so forth. 



The c.g.s. units here referred to are the so-called "electromagnetic" c.g.s. 

 units. The c.g.s. units of the "electrostatic system" are entirely ignored in this 

 text. 



Definition of the abohm. 

 A wire has a resistance of one 

 abohm when one erg of heat is 

 generated in it in one second 

 by a current of one abampere. 



Definition of the abvolt. 



An electric generator has an 

 electromotive force of one ab- 

 volt when it delivers one erg 

 per second of power with a 

 current output of one ab- 

 ampere. 



The abvolt may be defined 

 on the basis of Ohm's law as 

 the electromotive force between 

 the terminals of a resistance 

 of one abohm when a current 

 of one abampere is flowing 

 through it. 



Definition of the ohm. A 



wire has a resistance of one 

 ohm when one joule of heat is 

 generated in it in one second 

 by a current of one ampere. 

 The ohm is equal to io 9 

 abohms. 



Definition of the volt. An 

 electric generator has an elec- 

 tromotive force of one volt 

 when it delivers one joule per 

 second (one watt) of power 

 with a current output of one 

 ampere. The volt is equal to 

 io 8 ab volts. 



The volt may be denned on 

 the basis of Ohm's law as the 

 electromotive force between 

 the terminals of a resistance of 

 one ohm when a current of 

 one ampere is flowing through 

 it. 



14. The intensity of the magnetic field at the center of a 

 circular coil of wire. If we can calculate the force with which a 

 current in a circular coil of wire acts on a magnet pole of given 

 strength placed at the center of the circular coil, we can derive 

 an expression for the intensity of the magnetic field at the ceimr 

 of the coil due to the current in the coil, because the force exerted 



