ELECTRICAL UNITS. 



appreciable resistance, and that there is no other resistance in the 

 circuit than that of the wire which connects the two points A and 

 B. The resistance of this wire will be equal to the absolute unit, if 

 the bar, being equal to unit length, and moving in unit field with unit 

 velocity, perpendicular to the lines of force, gives rise to a current 

 capable of producing in the wire unit of energy per second in the 

 form of heat. 



Electromotive force [E]. The electromotive force is deduced 

 from Ohm's law 



and its dimensions are 



Capacity [C]. Capacity being the ratio of the quantity of 

 electricity which charges a condenser, to the difference of potential 

 of the two armatures, we have again 



or 



609. DIMENSIONS OF THE PRINCIPAL UNITS. We might in the 

 same way determine the dimensions of the other quantities which we 

 have not examined. We shall give in the following tables the 

 dimensions of the most important quantities. 



FUNDAMENTAL UNITS. 



Length ......... [L], 



Mass ...... . . . [M], 



Time ......... [T]. 



DERIVED MECHANICAL UNITS. 



Velocity . . ........ 



Acceleration ........ [LT~ 2 ], 



Force ........... [LMT" 2 ], 



Energy ......... [L 2 MT~ 2 ]. 



