Practice question

**Ohm's law deviation** at high fields occurs when τ or n vary with E, resistivity ρ = m/(n e² τ) changes, non-ohmic behaviour seen in semiconductors, electrolytes. At moderate fields, linear V-I holds, slope = R. For resistors R in series: Rₑq = R + R = 2R . In parallel: 1/Rₑq = 1/R + 1/R = 2/R ⇒ Rₑq = R/2 . The series resistance (2R) is four times the parallel resistance (R/2), as 2R / (R/2) = 4 . Applying I = n e A v_d, R = ρ l/A, R_t = R₀[1+αΔT], Kirchhoff's ΣI=0, ΣV=0, R_eq series/parallel, V = ε - I