Question

The amount of work done in blowing a soap bubble such that its diameter increases from d to D is : (surface tension of solution $=$ T)

• A. $4\pi (D^2-d^2)T$
• B. $8\pi (D^2-d^2)T$
• C. $\pi (D^2-d^2)T$
• D. $2\pi (D^2-d^2)T$

Answer 1

The correct option is D $2\pi (D^2-d^2)T$

New $SA=\pi D^2$
Old $SA=\pi d^2$
$\Delta U=2\pi (D^2-d^2)T$