
Lecture Description
Some strange and uncommon things occur in these adventures. For example: how can a gas which is HOT feel COLD? Let's look at some of these unusual things.
A. Here is an ordinary automobile tire - inflated. We agree that
the atmosphere is hot - the ground is hot - the tire is hot -
the air in the tire is hot. Now we depress the valve stem and out
comes some HOT air. But how does it feel? IT FEELS COLD!
IT IS COLD! That is - its temperature is lower the instant it
emerges.
B. There is a simpler demonstration of this strange business: The air
in my lungs is HOT. I now blow out some of this air from my
mouth. With my mouth wide open the air coming out IS HOT.
With my lips pursed as if to blow a whistle the air comes out
COLD! So - I am a strange creature: I can blow both hot and
cold!
C. Consider a CO2 fire extinguisher. We release the gas. The temperature drops so low that we get "CO2 snow".
D. We have a device which might well be called a SPUTNIK! It is
like a Hero's engine. A CO2 cartridge is lodged in a chamber -
the cartridge is pricked - the gas emerges - the Laws of Newton
play their proper role and the arm rotates. The gas comes out this—
a-way — the chamber goes that-a-way! Our interest here is this:
it is so cold that the water vapor in the room has condensed on it
and there is "frost" on the cartridge.
E. A cast-iron "bomb" is filled with water. ... filled completely with
the occluded gases first gotten rid of. We place this vessel in a
tub - a pail - of ice water. The water IN the chamber freezes.
The forces of expansion are tremendous and the "bomb" is shattered.
Dangerous to do! And we encounter this strange property of water:
that it expands when it freezes.
The forces arising in the expansion of a gas can be nicely shown with an Earth-bound Rocket. A steel pipe is tightly closed at one end. The pipe is filled with solid CO2 - "dry ice". The open end of the chamber is stoppered up. The CO2 goes into gas. The pressure increases. Out pops the stopper.
G. The Galilean Thermometer is an enchanting historical piece. A glass vessel of spherical shape has a one-hole stopper fitted to it with a glass tube. The vessel is held in a clamp upside down with the open end of the glass tube in a beaker of colored water. The air in the spherical vessel is cooled - say with ice put on it. The liquid in the lower beaker "climbs" up into the spherical chamber. If now with the column of liquid high in the tube the spherical vessel is warmed - as by placing the hand on it - the liquid is driven down. Here is an example of a higher column - a longer column - meaning a LOWER temperature! Nor must we forget the role that pressure plays in this demonstration. Galileo's thermo-meter was really a pressure-meter!
Course Index
- The Idea of the Center of Gravity
- Newton's First Law of Motion: Inertia
- Newton's Second Law of Motion: The Elevator Problem
- Newton's Third Law of Motion: Momentum
- Energy and Momentum
- Concerning Falling Bodies & Projectiles
- The Simple Pendulum and Other Oscillating Things
- Adventures with Bernoulli: Bernoulli's Principle
- Soap Bubbles and Soap Films
- Atmospheric Pressure
- Centrifugal Force and Other Strange Matters
- The Strange Behavior of Rolling Things
- Archimedes' Principle
- Pascal's Principle: The Properties of Liquids
- Levers, Inclines Planes, Geared-wheels and Other Machines
- The Ideas of Heat and Temperature
- Thermometric Properties and Processes
- How to Produce Heat Energy
- Thermal Expansion of Stuff: Solids
- Thermal Expansion of Stuff: Gases & Liquids
- The Strange Thermal Behavior of Ice and Water
- Heat Energy Transfer by Conduction
- Heat Energy Transfer by Convection
- Heat Energy Transfer by Radiation
- Evaporation, Boiling, Freezing: A Dramatic Adventure
- Miscellaneous Adventures in Heat
- The Drama in Real Cold Stuff: Liquid Nitrogen
- The Physics of Toys: Mechanical
- The Physics of Toys: Acoustic and Thermal
- Waves: Kinds of Properties
- Sound Waves: Sources of Sound & Pitch and Frequency
- Vibrating Bars and Strings: The Phenomenon of Beats
- Resonance: Forced Vibrations
- Sounding Pipes
- Vibrating Rods and Plates
- Miscellaneous Adventures in Sound
- Electrostatic Phenomena: Foundations of Electricity
- Electrostatic Toys, Part 1
- Electrostatic Toys, Part 2
- Adventures with Electric Charges
- Adventures in Magnetism
- Ways to "Produce" Electricity
- Properties and Effects of Electric Currents
- Adventures in Electromagnetism
- Further Adventures in Electromagnetism
- 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.