# Dictionary:Cole-Cole relaxation model

(kōl kōl) A model for induced polarization (IP) effects in which the effective impedance varies as a power of the frequency. The complex resistivity is given by

where *R*_{o} is the dc resistivity, is the time constant, and *c* is the frequency dependence. Typical ranges for parameters are *m*=0.1 to 1.0, depending on the mineral content, = 10^{-4} to 10^{4} depending on grain size, and *c*=0.2 to 0.6 depending on the particle size distribution. Compare *Warburg impedance*, for which the value of *c* is 0.5.