1.

A film of water is formed between two straight parallel wires of length 10 cm each separated by `0.5cm` If their separation is increased by `1mm` while still maintaining their parallelism, how much work will have to be done (Surface tension of water `=7.2xx10^-2(N)/(m)`)A. `7.22xx10^-6Joule`B. `1.44xx10^-5joule`C. `2.88xx10^-5joule`D. `5.76xx10^-5joule`

Answer» Correct Answer - B
Increment in area of soap film`=A_2-A_1`
`2xx[(10xx0.6)-(10xx0.5)]xx10^-4=2xx10^-4m^2`
Work done `=TxxtriangleA`
`=7.2xx10^-2xx2xx10^-4=1.44xx10^-5J`


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