# Dictionary:Metal factor (MF)

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 (ρ_{α} in ohm-feet) and multiplied by a constant:

**1**. Originally metal factor was defined as

where ρ_{dc} is the low-frequency resistivity and ρ_{ac} is the high-frequency resistivity in ohm-feet.

**2**. In the frequency domain the definition used is

**3**. In the time domain, the metal factor is

where *M* is chargeability in millivolt-seconds per volt and ρ_{dc} 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*):

The metal factor has units of conductivity. It is also called **metallic-conduction factor**.