Practice question

Given: A wire of length 15 m and cross-sectional area 2 × 10⁻⁶ m² has a resistance of 30 Ω . What is the resistivity of the material? These values define the system as per NCERT data. Formula: Resistance: R = rho l/A. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Rearrange: rho = R A/l . Substitute: rho = frac30 × 2 × 10⁻⁶¹⁵= 4 × 10⁻⁶Ω 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.