Figure 10.24 (a) shows a thin liquid film supporting a small weight = 4.5 × 10–2 N. What is the weight supported by a film of the same liquid at the same temperature in Fig. (b) and (c)? Explain your answer physically.

The surface tension =


Where,


‘F’ is the weight supported by the films,


‘l’ is the length of the liquid film.


From the equation, we can see that the surface tension only depends on the weight and the length of the film. The liquid is same and at the same temperature in all the three cases (a), (b), (c).


Thus, the surface tension will be same in all the three cases and thus, the weight supported by will be same in all the three cases i.e 4.5 × 10-2 N


18