The surface tension of liquid is 0.5 N/m. If a film is held on a ring of area 0.02 m2, its surface energy is

(a) 5×10-2 joule                         (b) 2×10-2 joule

(c) 4×10-4 joule                         (d) 0.8×10-1 joule

(b) Surface energy = T×A=0.5×2×(0.02)=2×10 -2J

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