Question:
A frame made up of metallic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by 25% the energy of the soap film will be changed by
A frame made up of metallic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by 25% the energy of the soap film will be changed by
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Surface energy of a film is proportional to its area, so the percentage change in energy equals the percentage change in area.
Updated On: Nov 12, 2026
- \(100\%\)
- \(75\%\)
- \(50\%\)
- \(25\%\)
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept
A soap film has two surfaces, so its surface energy is \(U=2TA\).
Step 2: Apply the Condition
\(T\) is constant, so \(U\propto A\).
Step 3: Calculation
Area reduced by 25% means \(\dfrac{\Delta U}{U}=\dfrac{\Delta A}{A}=25\%\).
Final Answer:
The energy of the soap film changes by 25%. \[ \boxed{\text{(D) }25\%} \]
A soap film has two surfaces, so its surface energy is \(U=2TA\).
Step 2: Apply the Condition
\(T\) is constant, so \(U\propto A\).
Step 3: Calculation
Area reduced by 25% means \(\dfrac{\Delta U}{U}=\dfrac{\Delta A}{A}=25\%\).
Final Answer:
The energy of the soap film changes by 25%. \[ \boxed{\text{(D) }25\%} \]
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