AIIMS 2017 Physics Cubical Expansion MCQ Question

To find the true barometric height at 0°C, we need to account for the thermal expansion of the brass scale. The scale reading at 30°C is 74.5 cm, which must be corrected for the temperature difference to 15°C (the reference point). The formula for linear expansion is ΔL = L₀αΔT, where L₀ is the original length (74.5 cm), α is the coefficient of linear expansion (which can be derived from the cubical expansion coefficient of brass), and ΔT is the change in temperature. After performing the calculations, the corrected height at 0°C is found to be 74.122 cm, making option A correct. Other options are incorrect as they do not accurately reflect the adjustments for thermal expansion based on the given coefficients.