Relevant Time Constant

The time constant that determines how long it will take the current flowing in the conductive material to reach steady state is given by t = e/s. In a good conductor such as steel (e = 9x10^-12, s = 1x10⁷), t = 9x10^-19 seconds. Steady state conditions are reached almost instantaneously and in such cases you should use the DC conduction solver to analyze the potential field.

On the other hand, for a good dielectric such as fused quartz (s = 1x10^-17), the time constant is on the order of 10⁵ seconds. There will be a significant period before steady state currents start to flow and you should use the electrostatic solver to analyze the electric field. For many materials in between, a complete analysis may require an electric transient field solution.