## Unit Of Current

That current which, flowing in a conductor 1 centimeter long, and of 1 centimeter radius, produces at the center of the arc a magnetic field of unit strength.

This unit is ten times the ampere.

## Unit Of Potential

Unit difference of potential exists between the ends of a conductor, when the expenditure of 1 erg per second will cause unit current to flow.

This E.M.F. is equal to one hundred-millionth of a volt.

### Note

The erg = work done by a force of 1 dyne through a distance of one centimeter = 0.001019 gramme - cent = 0.00000007386 foot-lb. (London).

Unit of Resistance is that resistance which requires unit difference of potential to cause unit current to flow.

This resistance is 1,000-millionth of an ohm.

For ready reference the units most frequently used in practice are tabulated below, together with their value in C.G.S. absolute units.

 Electrical Quantity. Name of Unit. Dimensions of Unit. Value in C.G.S. Units. Resistance Ohm LT -1 109 C.G.S. units. Current Ampere L½M½T -1 10-1 " " Electrical pressure........ Volt. L3/2M½T -2 108 " " Energy. L2MT -2 107 " " Capacity Farad L-1T2 10-9 " " Capacity Microfarad 10-15 " " Power Watt L2MT -3 107 " " Power Kilowatt. 1010 " " Work. Watt-hour 109X36 " Work. Kilowatt-hour 1012X36 "