Practice question

Given: A conductor has a resistivity of 1.2 × 10⁻⁷Ω m and α = 4 × 10⁻³°C^{-1 at 20° C . What is its resistivity at 80° C ? These values define the system as per NCERT data. Formula: Use: rho_t = rho_0 [1 + α (T - T_0)]. This is standard NCERT relation. Substitution & Calculation: Substitute: rho_t = 1.2 × 10⁻⁷[1 + 4 × 10⁻³(80 - 20)] . Calculate: rho_t = 1.2 × 10⁻⁷[1 + 0.24] = 1.2 × 10⁻⁷ × 1.24 = 1.488 × 10⁻⁷Ω m . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.