A steel wire of length 2.7m and cross-sectional area 3×10−6m2 is stretched by a force of 450N. If the Young's modulus of
Stress: Stress = FA = 4503×10−6 = 1.5×108N/m2. Young's modulus: Y = StressStrain. Strain: Strain = StressY = 1.5×1082×1011 = 7.5×10−4. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 7.5×10−4. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
Ref: University Physics, Chapter 17: Thermal Expansion.
