Page:Electricity (1912) Kapp.djvu/85

as oil, glass, mica or paper, it is $K$ times smaller. This means that to bring a unit of positive charge to our sphere through such a medium takes $K$ times less energy than to bring it through air. In other words, to obtain the same charge an e.m.f. $K$ times smaller is sufficient, or, if the e.m.f. is the same, the resulting charge will be $K$ times larger. Hence by using a dielectric other than air the capacity of our condenser is increased $K$ times. The following table gives the value of $K$ for some dielectric materials—

Values of the Specific Inductive Capacity K in the C.G.S. Electrostatic System

Material

Glass

Mica

Insulating Oil used in transformers

Paraffin Wax

India Rubber

Gutta Percha

Paper, as used for power cables

Paper, as used in telephone cables

Paper, paraffined, as used in condensers

Distilled Water

Pure Alcohol

K

2—10

5—6

2—1

2.3

2.2—2.8

2.5—4

2.6—3.5

2—2.5

7.2

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