ELECTRICITY. 



41 



+ unit of electricity from one point to the other against the electro- 

 motive force. 



The C.G.S. unit of capacity (C) is the capacity of a condenser 

 which when charged with one C.G.S. unit of quantity is raised to 

 unit potential. 



The C.G.S. unit of resistance is the resistance of a conductor 

 such that unit difference of potential between its two extremities 

 causes a unit-current to flow through it. 



jDimensions. 



/ = intensity of field x length! 

 Q = current x time 



Current 

 Quantity 

 Potential 

 Electromotive force 



Resistance 

 Capacity 



E = work -~ quantity 



R electromotive force -~ 



current 

 - quantity 4- potential 



(54) RATIO OF TUE ELECTROSTATIC AND ELECTROMAGNETIC 

 UNITS. 



If the dimensions of the electrostatic units be divided by those of 

 the electromagnetic units, the ratio is found to be expressed by a 

 velocity, that is to say by a length divided by a time, by the 

 reciprocal, by the square, or by the square of the reciprocal of this 

 velocity. 



Unit. Electrostatic. Electromagnetic. Ratio. 



Quantity 

 Potential 



Capacity 

 Resistance 



L~ 1 T 



LT~ l 





This velocity -, = o> is found to be 2 '9857 x 10 10 cms. per 



second, which is nearly equal to the velocity of light, and about 30 

 times the velocity representing the ohm (see next page). 



(55) RELATIONS BETWEEN THE UNITS IN EACH SYSTEM. 

 For Electrostatics : 



force = which gives q if the unit of force and the distance 



JL" 



between the quantities of electricity be given *, 



