Practice question

Given: A steel rod has a length of 1 m at 20° C . What will be its length at 120° C if the coefficient of linear expansion of steel is 1.2 × 10⁻⁵ K^{-1 ? These values define the system as per NCERT data. Formula: Given: L_0 = 1 m, T_1 = 20° C, T_2 = 120° C, α_l = 1.2 × 10⁻⁵ K^{-1. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Δ T = 120 - 20 = 100° C . Linear expansion: Δ L = L_0 α_l Δ T = 1 × 1.2 × 10⁻⁵ × 100 = 1.2 × 10⁻³ m . New length: L = L_0 + Δ L = 1 + 0.0012 = 1.0012 m . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.