Some of the important properties of insulator (or dielectrics) are as under :
1. Resistance of an insulator is extremely high, conductivity is very small.
2. It does not conduct electricity.
3. Insulators have 8 electrons in the outer orbit.
4. The concentration of free electron is extremely small (~ 107 electrons/m3).
5. Insulators permit penetration of electromagnetic (EM) waves.
6. In good insulators alternation of EM waves is negligible.