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Question

What is the excess pressure inside a helium drop of radius 1mm at −270∘C? (Surface tension = 0.000239N/m)

Options

Choose one · Correct answer highlighted

Explanation

Excess pressure: ΔP = 2Sr. S = 0.000239N/m, r = 1×10−3m. ΔP = 2×0.0002391×10−3 = 0.478Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.48 Pa. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.