Electrical conductivity, σ, as a function of pressure for different planetary models. We show ages of t ≃ 0.4 (dots), 1.1 (dashes), and 5 Gyr (solid lines) for a planet with M = 1 M_j, showing two cases, T_eq = 1500, 2000 K, without (black, grey) and with Ohmic heating, parameter υ_avg = 3000 and 356 m/s, respectively (blue, red). We also show (brown and gold lines), for comparison, the simplified K⁺ -only thermal ionisation formula, which neglects pressure ionisation, for the cases without Ohmic heating.