Igneous rocks are formed through the cooling and solidification of magma. It undergoes changes in temperature and pressure that causes it to cool, solidify, and crystallize.
In a RC circuit we call time constant to the product of the resistance times the capacitance, which represents the time when the charge reaches to the 63% of the final value, as follows:
If we have a new circuit with new values for R and C, the time constant will be defined in the same way, as follows: