Displacement current and bounded electrical charges are responsible for rock polarization. Dielectric constant: Debye, Cole–Cole or Havriliak–Negami models. Three types of bulk polarization: polarization due to dipoles, ionic polarization, and electronic polarization. Interface polarization on grain boundaries is explained by the Maxwell–Wagner effect. At grain boundaries in contact with electrolyte fluid, electrical double layer is described by the Gouy–Chapman–Stern model. Reaction mechanisms between SiO2 and H2O may take place. Increased electrolyte concentration results in increased surface energy. Electrical flux density and dielectric losses. Dielectric properties of rocks. Energy transport, transmission and reflection coefficients of minerals for electromagnetic waves in rocks. Induced polarization of rocks. Mixing models for dielectric constant: effective medium approach, Wiener and Hashin–Shtrikman bounds, Lorenz equation and percolation model. Factors causing induced polarization in rocks and the Pelton model. Focus Box 9.1: Maxwell’s equations. Focus Box 9.2: Lorenz field and Clausius–Mossotti equation. Focus Box 9.3: Redox reactions, Warburg impedance, Nyquist plots.

Maxwell's discovery of the equations for the electromagnetic field was one of the greatest achievements of nineteenth-century physics. The laws of electrostatics, magnetostatics and the magnetic fields produced by steady currents were established by the 1820s. Faraday's discovery of electromagnetic induction in 1831 led to his concept of magnetic field lines and the visualisation of the laws of induction as being determined by the rate of cutting of the field lines. Maxwell mathematised Faraday's model of magnetic field lines by adopting a mechanical model of the aether. His theoretical investigations led to the introduction of the displacement current and the discovery that light is electromagnetic radiation.