Practice question

**Current and drift relation** I = n e A v_d shows current proportional to drift velocity and area. For A=6×10⁻⁷ m², I=1.8 A, n=8.5×10²⁸ m⁻³, v_d =1.8/(8.5×10²⁸×1.6×10⁻¹⁹×6×10⁻⁷)=2.2×10⁻⁴ m/s, illustrating small drift speed even for ampere currents. In semiconductors, as temperature rises, more electrons are thermally excited from the valence band to the conduction band, increasing the number of charge carriers ( n ). Since rho = m / (n e² tau) , a significant increase in n outweighs the decrease in tau , reducing rho and thus resistance. Applying I = n e A v_d, R = ρ l/A, R_t = R₀[1+αΔT], Kirchhoff's ΣI=0, ΣV=0,