Site for children

J. Perelman
"Entertaining physics". Book 1.
Chapter 6. Thermal phenomena


If now we ask, what is the height of the Eiffel tower, before answering: “300 meters”, you will probably ask:

- In what weather is cold or warm?

Due to the height of such a huge iron structure may not be the same at any temperature. We know that iron rod length 300 m extends to 3 mm when heated by one degree. Approximately the same number should increase and the height of the Eiffel tower when the temperature increases by 1°. In warm Sunny weather, the iron tower material can be heated in Paris C to +40, whereas in cold, rainy day temperature drops to +10°. and in the winter to 0°, even up to - 10° (severe frosts in Paris rare). As you can see, temperature can reach 40 degrees or more. Hence, the height of the Eiffel tower can vary by 3 * 40 = 120 mm, or 12 cm (greater than the length of this string).

Direct measurements have even found that the Eiffel tower is even more sensitive to temperature fluctuations than the air, it heats up and cools down faster and earlier reacts to the sudden appearance of the sun on a cloudy day. Change the height of the Eiffel tower were detected using the wire from a special Nickel steel, with almost no ability to change its length with temperature fluctuations. Wonderful alloy this is called “Invar” (from the Latin “unchanged”).

So, on a hot day the top of the Eiffel tower rises higher than in the cold, on a piece equal to the length of this string and made of iron, which, however, is not a single extra penny.

Entertaining physics J. Perelman


System Orphus


Did you like our site and you would like to support it? It's very simple: tell your friends about us!

  © 2014 All children