Question

A film of water is formed between two straight parallel wires of length 10cm each separated by 0.5 cm. If their separation is increased by 1 mm while still maintaining their parallelism how much work will have to be done ofwater (Surface tension of water $=(7.2 \times 10^{-2} \,N/m$ )

• A. $7.22 \times 10^{-6}\,J$
• B. $1.44 \times 10^{5}\,J$
• C. $2.88 \times 10^{-5}\,J$
• D. $5.76 \times 10^{5}\,J$

Answer 1

Answer: (B)

$1.44 \times 10^{5}\,J$

Answer 2

$W = 2T \times \Delta A \, \Rightarrow \, 2T [ 1(b_2 - b_1)]$