Most of the stuff in Nature expands when heated. And we have some wonderful and exciting demonstrations of this. In some cases some enchanting questions arise
A. The classical ball-and-ring demonstration: We have a metal ring - brass - and a metal sphere - also brass. At room temperature we show that the ball does not go through the ring. So we say the ring is too small OR the ball is too big! Now we heat the ring and presto - the ball now goes through. We say the ring got bigger OR the hole got bigger! We must UNDERSTAND exactly what is going on here!
B. We now have some metal plates - round ones - square ones - rectangular ones - and in each is a hole - a tiny tiny hole in some. Now we heat these plates uniformly - as we could do in an oven - and we ask: What does the tiny hole do? There are only three cases: The hole does nothing. The hole gets smaller. The hole gets bigger. And I leave it as an enchanting exercise for you all to contemplate! I might give a HINT: The ring which we first used in the ball-and-ring demonstration is really a plate with a big hole! Got it now?
C. We have a metal ring - no need to say EXACTLY CIRCULAR. And this ring has a diameter of its own stuff. We now heat this ring uniformly - as in the oven of my stove. Question: does the ring preserve its circularity or does it warp? Good question! Suggestion! Those of you who think one thing should try to convince those who think another! This is real intellectual inquiry.
D. A bimetallic strip consists of two metals fixed to each other along their length. We heat the strip. Let us say one metal is iron - the other brass. We see the strip bend. Question: does it bend toward the iron or toward the brass. A question for mathematical proof: If both strips are of equal thickness d the straight bimetallic strip will bend into a circle
E. We have two rods - both look like glass. One - we say - IS glass; the other is quartz. We heat these to red-hot in a flame. NOTE: while heating we see a color in the flame. Color is a thermometric process. Then we immerse them both in a beaker of COLD water. The glass shatters. The quartz does not. The quartz has a very small temperature coefficient of expansion.
F. We introduce an interesting question: Consider one rail of the RR track between Los Angeles and San Francisco. Let it be 400 miles long - in one continuous strip. No breaks. Let this rail suffer an overall change in temperature of - say 25°C. QUESTION: How much expansion does this 400-mile rail suffer? ANSWER: Nearly 600 feet! Hard to believe but easy to prove:
G. Why does popcorn pop? A kernel of un-popped corn looks dry - lifeless - inert - dead! But it is not dry! and it is not dead! When we heat it the very tiny - very minute - bit of water which is in it EXPANDS enormously - some 1700 times! The forces are staggering!
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.