Soap Bubbles and Soap Films 
Soap Bubbles and Soap Films
by Prof. Miller
Video Lecture 9 of 46
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Date Added: February 5, 2015

Lecture Description

Soap Bubbles and Soap Films are not for child's play alone. Their study reveals some very important principles of Nature. Principal among these is this: That the Energy of a System tends toward Least. That is - the Energy of a System left to itself goes downhill. This is why raindrops are spherical; this is why a drop of water or a drop of mercury flattens out when it gets bigger. We show an array of exciting things:

A - THE DOUBLE BUBBLE PARADOX: We blow a small soap bubble and a big_ soap bubble simultaneously. Then we allow the two to be connected with each other. And a most remarkable thing happens! The SMALL one blows the BIG one bigger! We thus discover that the pressure in the smaller bubble is the greater. Which is NOT what most people think!

B - We fill a vessel very very full with water - so full in fact that it is
"humped up" high above the edge of the vessel. The surface behaves as a tight membrane - a stretched film - and is so strong in fact that we can float a steel needle on it!

C - We show some mercury droplets on a clean glass plate. When small they
are round; when bigger they flatten out. When two bubbles are brought very near to each other they coalesce - that is - they swiftly go together and become one. This action is incredibly swift and is most certainly electrical in nature.

D - We show an array of wire frames of various geometries dipped into a vat of soap solution. The soap films formed are very beautiful to see. When any one is punctured - broken - all the rest quickly take up a form such that the Energy of the System is again a minimum.

E - A circular frame has a loose string across a diameter. A soap film is formed covering the frame and the string. When the film is punctured at any spot the string instantly goes into a circular arc since a circular shape represents least Energy.

F - When a narrow small-bore tube - like a glass-tube - is dipped into water the water climbs INSIDE the tube higher than it is outside the tube. When this is done with mercury the mercury inside the tube is lower than the mercury level outside the tube. And the surface of the water is concave upward whereas the surface of the mercury is concave downward" We show this surface curvature with two wedge-shaped vessels.

Soap Films and Soap Bubbles and Drops are wonderful to play with and exciting to explore. Everyone - young and old - should read SOAP BUBBLES by C.V. Boys. Professor Boys describes hundreds of experiments which can be done at home or in school with utterly simple apparatus.

Course Index

  1. The Idea of the Center of Gravity
  2. Newton's First Law of Motion: Inertia
  3. Newton's Second Law of Motion: The Elevator Problem
  4. Newton's Third Law of Motion: Momentum
  5. Energy and Momentum
  6. Concerning Falling Bodies & Projectiles
  7. The Simple Pendulum and Other Oscillating Things
  8. Adventures with Bernoulli: Bernoulli's Principle
  9. Soap Bubbles and Soap Films
  10. Atmospheric Pressure
  11. Centrifugal Force and Other Strange Matters
  12. The Strange Behavior of Rolling Things
  13. Archimedes' Principle
  14. Pascal's Principle: The Properties of Liquids
  15. Levers, Inclines Planes, Geared-wheels and Other Machines
  16. The Ideas of Heat and Temperature
  17. Thermometric Properties and Processes
  18. How to Produce Heat Energy
  19. Thermal Expansion of Stuff: Solids
  20. Thermal Expansion of Stuff: Gases & Liquids
  21. The Strange Thermal Behavior of Ice and Water
  22. Heat Energy Transfer by Conduction
  23. Heat Energy Transfer by Convection
  24. Heat Energy Transfer by Radiation
  25. Evaporation, Boiling, Freezing: A Dramatic Adventure
  26. Miscellaneous Adventures in Heat
  27. The Drama in Real Cold Stuff: Liquid Nitrogen
  28. The Physics of Toys: Mechanical
  29. The Physics of Toys: Acoustic and Thermal
  30. Waves: Kinds of Properties
  31. Sound Waves: Sources of Sound & Pitch and Frequency
  32. Vibrating Bars and Strings: The Phenomenon of Beats
  33. Resonance: Forced Vibrations
  34. Sounding Pipes
  35. Vibrating Rods and Plates
  36. Miscellaneous Adventures in Sound
  37. Electrostatic Phenomena: Foundations of Electricity
  38. Electrostatic Toys, Part 1
  39. Electrostatic Toys, Part 2
  40. Adventures with Electric Charges
  41. Adventures in Magnetism
  42. Ways to "Produce" Electricity
  43. Properties and Effects of Electric Currents
  44. Adventures in Electromagnetism
  45. Further Adventures in Electromagnetism
  46. Miscellaneous and Wondrous Things in E&M

Course Description

Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics. The series was also released in the United States under the title Science Demonstrations.

This program was a series of 45 shows (approximately 15 minutes each) on various topics in physics, organized into 3 units: Mechanics; Heat and Temperature / Toys; and Waves and Sound / Electricity and Magnetism.


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