Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What are some of these scales based on?

  1. Dec 3, 2003 #1


    User Avatar
    Science Advisor

    There are a few units that I'm interested in understanding a little better; mainly in understanding what they are based on. For example, 1 calorie is the energy to change the temperature of 1kg of water by 1C (IIRC).
    Here are the units I don't understand too well.

    reaumure - temperature
    torr - pressure
    bar - pressure

    I've already tried to get the info myself. For reaumure, I end up with a bunch of sites in French which doesn't help since I can't read French. Searching for the pressure ones lead me to a bunch of sciences questions/tests posted online.
  2. jcsd
  3. Dec 3, 2003 #2
    you know it is said that french is the language of love...
    hope this helps a bit

    and more
    Last edited: Dec 3, 2003
  4. Dec 3, 2003 #3

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    Small technical detail: the calorie (with a small c) is the heat required to raise one gram of water by one degree C. The Calorie (with a large C) is a "nutritional calorie" which is actually a kilocalorie. THis is what follows your description above, but it is not the calorie used by scientists.

    The "bar" has come up in the recent past on a few threads in this forum. IT is defined as the pressure created by "one million dynes of force on one square centimeter." THis is equivalent to 10 newtons of force on one square centimeter. THis is the same as 100,000 newtons of force on one square meter which makes one bar exactly 100,000 pascals. The bar is a very convenient unit because one bar is very close to atmospheric pressure (ATM = 1.01 bar).

    One bar is also close to the common European pressure unit of kilograms per square centimeter. THis unit is scientifically incorrect, but it is what is written on a lot of bicycle pumps.
  5. Dec 3, 2003 #4
  6. Jul 22, 2008 #5
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?