Video Cassette ("Loops")

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For teachers who are not familiar with the "Loops," a few words of explanation may be in order. When the IPS "Super-8" film loops were first produced about 25 years ago, the four-minute time constraint challenged the ingenuity of the IPS Group. In four minutes all the essential parts of every demonstration had to be shown, data had to be collected, and, in some cases, graphed to arrive at conclusions. The equipment had to be simple to encourage teachers and students to do the demonstrations themselves. The result was a collection of film loops unsurpassed in clarity and conciseness even in this age of computer-interfaced demonstrations. Far from being a disadvantage, the absence of sound lets teachers add their own comments or questions as they see fit.

The first three loops on the cassette are in the order in which they appear in the Seventh Edition, although they are equally useful with earlier editions. Those teachers who have not yet upgraded to the Sixth Edition of IPS will find Loops 4-7 relate to Chapter 12 of the Fifth Edition. Loops 8-10 will enrich any course addressing the kinetic theory of gases.

Contents:
  1. Radioactive Substances I Shows how Figure 7.2 in the Sixth Edition is produced from Figure 7.1. It also checks the same six substances with a Geiger counter.


  2. Radioactive Substances II Shows the construction and operation of a diffusion cloud chamber (Figure 7.12).


  3. Motion of Electric Charges in Vacuum Takes apart a diode and demonstrates under what conditions a current will flow through the diode (Figures 12.9?12.13).
  4. Molecular Motion and Diffusion A most convincing demonstration of how differently a drop of bromine evaporates in the presence of air and in a vacuum.
  5. A Sphere-Gas Machine Shows qualitatively the relation between volume and pressure, and between volume and temperature for a "gas" made of small steel spheres.


  6. How Does the Thermal Expansion of Gases Compare? The thermal expansion of equal volumes of three gases is simultane-ously observed over the same temperature range. The readings for all three gases are shown to lie on the same curve.


  7. How Does the Thermal Expansion of Liquids Compare? The thermal expansion of equal volumes of three liquids is simultane-ously observed over the same temperature range. The readings for the three liquids are shown to lie on different curves.

  8. A Disk Gas (An Analog) Introduces the operation of a unique "puck table" on which the floating pucks are kept in motion by vibrating pucks on the boundary, providing a much better analog than other puck tables to a real gas in a container.


    9.
  9. The Distribution of Speeds in a Mixture of Disk Gases Measures the distribution of speeds of a mixture of pucks representing two gases of different molecular mass at the same "temperature." The lighter pucks are shown to have a higher average speed.


  10. How does the Effusion Time of Gases Compare? Compares the effusion time of equal volumes of carbon dioxide and hydrogen and raises the question of the relation between these times and the molecular masses of the two gases.