Practice question

**Conductivity** σ=1/ρ decreases with temperature for metals, σ = n e² τ/m, τ ∝1/T due to lattice vibrations. For semiconductors, n increases exponentially with T, so σ increases, opposite to metals, explaining why metallic resistance rises with temperature. Total resistance: Rtₒtₐl = 6 + 2 = 8 Ω . Current: I = (ε/Rtₒtₐl) = (8/8) = 1 A . Terminal voltage: V = ε - I r = 8 - 1 × 2 = 6 V . 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 r and P =