સાબુના પરપોટાની સપાટીનું પૃષ્ઠતાણ \(2.0 \times 10^{-2} \;Nm ^{-1}\) છે. સાબુના પરપોટાની ત્રિજ્યાને \(3.5 \;cm\) થી \(7\; cm\) સુધી વધારવા માટે કરવામાં આવેલ કાર્ય \(.........\times 10^{-4}\,J\) હશે. [\(\pi=\frac{22}{7}\) લો]

A \(0.72\)
B \(5.76\)
C \(18.48\)
D \(9.24\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(18.48\)

Step-by-step Solution

Detailed explanation

Surface area of soap bubble \(=2 \times 4 \pi R^2\) Work done \(=\) change in surface energy \(\times T_S\) \(= T _{ S } \times 8 \pi \times\left( R _2^2- R _1^2\right)\) \(=2 \times 10^{-2} \times 8 \times \frac{22}{7} \times 49 \times \frac{3}{4} \times 10^{-4}\)…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

સૂચિ - I	સૂચિ - II
(A) સમદાબ	(I) ΔQ = ΔW
(B) સમકદ	(II) ΔQ = ΔU
(C) સમમોષ્મી	(III) ΔQ = zero
(D) સમતાપી	(IV) ΔQ = ΔU + PΔV

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