In normal metals the collision time is typically  s, so for frequencies < 100 GHz  is very small and can be ignored; then this equation reduces to the DC conductance . Kinetic inductance is therefore only significant at optical frequencies, and in superconductors whose .
For normal metals, the collision time is typically very small (approximately s) for frequencies less than 100 GHz, leading to a simplified equation of DC conductance. Kinetic inductance is significant primarily at optical frequencies and in superconductors that display this characteristic.