A nichrome wire has a resistance of \( 90 \, \Omega \) at \( 20^\circ \text{C} \) and \( \alpha = 1.7 \times 10^{-4} \,
**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. Use: R_t = R₀ [1 + α (T - T₀)] . Substitute: R_t = 90 [1 + 1.7 × 10⁻⁴ (260 - 20)] . Calculate: R_t = 90 [1 + 1.7 × 10⁻⁴ × 240] = 90 [1 + 0.0408] = 90 × 1.0408 = 93.67 Ω . 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 =
Ref: NCERT > Physics Book > Current Electricity > Resistance, Resistivity and Ohm's Law