Question

Surface tension of a liquid is 5 $N/m$. If its thin film is made in a ring of area $0.02m^2$, then its surface energy will be :

• A. $5\times {10}^{-3}$ Joule
• B. $2.5\times {10}^{-3}$ Joule
• C. $1\times {10}^{-1}$ Joule
• D. $5\times {10}^{-1}$ Joule

Answer 1

The correct option is D $5\times {10}^{-1}$ Joule

The surface energy in any fluid is given as the product of the surface tension of the fluid times the area on which this surface tension is acting.

Since, this is a ring with area $0.02m^2$ and there are 2 surfaces to it, therefore, the total area = $0.04m^2$

Hence, the total surface energy would be,

$U=TA$

$U=5\times 0.04=0.2J$