1-19
Common insulating materials for capacitors and their dielectric constant are:
MATERIAL
CONSTANT
Vacuum
1.0000
Air
1.0006
Paraffin paper
3.5
Glass
5 to 10
Mica
3 to 6
Rubber
2.5 to 35
Wood
2.5 to 8
Glycerine (15º C)
56
Petroleum
2
Pure Water
81
The time to charge a capacitor to 63.2 percent of applied voltage or discharge it to 36.8 percent of its
initial voltage is known as the TIME CONSTANT (t) of the circuit. Figure 1-11 shows an RC time
constant chart. One time constant (t) in seconds equals R
C, with R in ohms and C in farads.
