# Dictionary:Metal factor (MF)

Other languages:

A measure of the total frequency-dependent change in conductivity or capacitivity of a rock, used in the interpretatation of IP data. Metal factor is the percent-frequency-effect (q.v.) normalized by dividing by the measured resistivity (ρα in ohm-feet) and multiplied by a constant:

$MF=2\pi 10^{3}{\frac {(PFE)}{\rho _{\alpha }}}$ 1. Originally metal factor was defined as

$MF=2\pi 10^{5}({\frac {\rho _{dc}-\rho _{ac}}{\rho _{ac}-\rho _{dc}}})$ where ρdc is the low-frequency resistivity and ρac is the high-frequency resistivity in ohm-feet.

2. In the frequency domain the definition used is

$MF=2\pi 10^{5}{\frac {\rho _{dc}-\rho _{ac}}{\rho _{dc}\rho _{ac}}}$ 3. In the time domain, the metal factor is

$MF={\frac {2000M}{\rho _{dc}}}$ where M is chargeability in millivolt-seconds per volt and ρdc is in ohm-meters. This unit is similar to Keller’s parameter, specific capacity (q.v.) or static capacity.

4. A constant times the ratio (sometimes called electric susceptibility or capacitivity) between induced-current dipole moment per unit volume (P) and electric field (E):

$MF={\frac {2\times 10^{6}P}{E}}$ The metal factor has units of conductivity. It is also called metallic-conduction factor.