38. 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 (Surface tension of water =7.2 x10^-2 N/m)

(a) 7.2 x 10^-6 Joule                  (b) 1.44 x 10^-5 Joule

(c) 2.88 x 10^-5 Joule               (d) 5.76 x 10^-5 Joule

Ans. b

(14)