Q. A square wire frame of size L is dipped in a liquid. On taking out a membrane is formed. If the surface tension of liquid is T, then the force acting on a frame will be
A) $2\ T/L$
B) $4T/L$
C) $8\ T/L$
D) $16\ T/L$
Explanation
(c) Since the wire frame is dipped in liquid, therefore its membrane has two free surfaces. Total length of square wire frame in contact of membrane
$= 2 \times perimeter\ of\ square = 2 \times 4L = 8L$
Hence, force acting on a frame
$F = Tl = T \times 8L = 8L$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.