A thin liquid film formed between a `U-`shaped wire and a light slider supports a weight of `1.5 xx 10^(-2)N`(see figure). The length of the slider is `30 cm` and its weight negligible. The surfaces tension of the liquid film is :

Options

A. `0.025 Nm^(-1)`
B. `0.0125 Nm^(-1)`
C. `0.1 Nm^(-1)`
D. `0.05 Nm^(-1)`

Answer

A

Explanation

For a liquid film, the force of surface tension is given by `F=2l xx T`.
The force of surface tension acting on the wire balanes the force due to the weight W.
`F=T xx 2l=W`
`rArr 2T(0.3)=1.5 xx 10^(-2)`
`rArr T=2.5 xx 10^(-2)N//m`