Read Charged Conductors: Conserve Charge, Then Rescale Radius
When a conducting soap bubble becomes one drop, total charge is conserved but radius follows volume conservation. The new potential follows Q/(4 π ε₀ R).
Electricity questions depend on identifying charge, a conducting path and the condition that controls current or magnetic effect.
Start with the condition
Find drop radius from four-thirds π R-cubed equal to film volume. Then use the initial bubble potential to express its total charge before calculating the drop potential.
Build the governing relation
The two bubble surfaces and thin-film geometry determine the initial capacitance; do not replace it immediately with a solid sphere.
Finish with a physical check
Check the limiting case before selecting an option: remove the special feature in the diagram or make the relevant parameter very large or very small. The result should reduce to a familiar relation.
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- ✓State the physical condition before choosing a formula.
- ✓Keep direction, sign and constraint information explicit.
- ✓Test one limiting case before committing to an option.
Conserving potential during bursting is wrong—the isolated conductor conserves charge.
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