A steel wire of length 3.0m and cross-sectional area 2×10−6m2 is stretched by a force of 200N. If the Young's modulus of
Young's modulus: Y = FLAΔL. Rearrange: ΔL = FLAY. Substitute: ΔL = 200×3.02×10−6×2×1011 = 6004×105 = 1.5×10−3m = 1.5mm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.5mm. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: University Physics, Chapter 17: Thermal Expansion.
