Thermometric Properties and Processes
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Video Lecture 17 of 46
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### Lecture Description

We ask: By what physical properties or processes can we investigate the nature of HEAT and TEMPERATURE? What does NATURE do to demonstrate changes in temperature?

A. Expansion is a thermometric process. Evidence: a mercury-in-
glass thermo-meter — note the spelling! - shows an expanding
length of mercury column when the thermometer is immersed in
hot water - say.

B. Electrical Resistance is a thermometric property. We show a coil
of wire connected in series with an automobile lamp and a car battery. At room temperature the coil resistance is such that the lamp
lights at normal brightness. If now we put some ice - or "dry ice"
- solid CO2 - on the coil - the lamp lights brighter. On the
other hand if we heat the coil with a flame the light goes dimmer.
The mathematical expression for the behavior of a coil - of a metallic conductor - is this:
Rt = Ml +c^) where «C is called the temperature coefficient of resistance. For most metallic conductors this has the value 0.00366 - which comes out to be very nearly 1/273. This reveals that the electrons in a wire behave very much like the molecules In a gas! A very exciting thing to discover!

C. Magnetism is a thermometric property. If a bar of magnetic material
- iron - say - is held by a magnet and the bar is heated - the
magnetic forces get less. Roughly speaking this suggests the follow¬
ing: A magnetized sample of stuff implies an orderly arrangement of
the elementary parts. When heated a state of disorder arises.

D. Thermoelectric "power" is a thermometric process. If we connect
any two different wires and have their junctions at different temperatures a difference of potential arises and an electric current
ensues. We show an array of thermocouples - one whose scale is
thermometric - that is - it reads in degrees.

E. Color is a thermometric property. If we lay out on a clean fresh snow bank an array of colored sheets of paper - in the full sun -we see an astonishing thing: the paper sinks in the snow - mean¬ing of course that the snow is being melted underneath. And the different colored sheets sink at different rates.

### 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.