A frame made of metalic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by `50%` the energy of the soap film will be changed by:

Options

A. `100%`
B. `25%`
C. `90%`
D. `75%`

Answer

C

Explanation

Surface energy = surface tension `xx ` surface area ` E = T xx 2A `
New surface energy,
` E _ 1 = T xx 2 (( A)/ ( 10)) =T xx A// 5 `
% decrease in surface energy
` = ( E - E _ 1 )/( E) xx 100 = (2TA -TA// 5 ) /( 2T A ) xx 100 `
` = 90% `