A circular film of a liquid has an area of 10 ~cm ^2 . If the work done in making its radius two times the initial radius is 8 10⁻³ ~J . the surface tension of the liquid is (1+ 1 ) Nm ⁻¹ . The value of is

Step-by-step solution

If radius ( r ) of a circle made two times (2r) aligned then change in area & = (2 r)^2- r^2 & =3 r^2=3 initial area aligned Here, initial area of soap film, A₁=10 ~cm ^2 Final area has a radius twice that of initial radius. So, change in area aligned A & =3 A₁=3 10 ~cm ^2 & =3 10 10⁻⁴ ~m ^2 & =3 10⁻³ ~m ^2 aligned As, a liquid film has two surfaces (one top and other bottom). Change in surface energy or work done, aligned W & =2 A T T & = Surface tension T & =W / 2 A aligned Here, W=8 10⁻³ ~J A=30 10⁻³ ~m ^2 So, s