The reciprocal of Avogadro's constant is numerically equal to the Won't find it playing any role in any law or theory about stars, You find it only by countingĪtoms or molecules in something of known relative molecular mass. You won't discover its value experimentally byĬounting stars, grains of sand, or people. The value ofĪvogadro's number found in handbooks is an experimentallyĭetermined vlue, and is an approximation limited by the accuracy However, must be determined experimentally. No experiment of science can everĭetermine their value, except approximately. Though these are used in science, their definitionsĪre independent of science. "You could have a mole of stars, grains of sand, or people." In science weĭo use entities that are just numbers, such asģ, 100, etc. Is Avogadro's constant just a number? What about those textbooks that say This affects their quoted values for the universal gas constant Prefer to use the kilogram-mole, or worse, use it and the As Mario Iona reminds me, SI is not simply a MKS system. Though it seems inconsistent, the SI base unit of Avogadro's number is the gram-mole. Has units further convinces us that it is not "merely a number." When the kilogram-mole is used, Avogadro's constant shouldīe written: 6.02252 × 10 26 kmol -1. The unit name for a kilogram-mole is kmol. The unit name for a gram-mole is simply mol. One must specify whether the value of Avogadro's constant is This can beĬonfusing and misleading to students who are conscientiously trying to Some older books call this value Avogadro's number,Īnd when that is done, no units are attached to it. That the number of particles in a gram-mole is 6.02 × 10 23. Who hasn't the foggiest idea what action is.Īlso see Heisenberg's uncertainty principle.Īvogadro's constant. Textbooks in meaningless statements of Newton's third law: "ActionĮquals reaction." This statement is useless to the modern student, Unfortunately the word action persists in Special relation to each other, expressed in Heisenberg's Whose product has dimensions of energy×time are calledĬonjugate quantities in quantum mechanics, and have a Planck'sĬonstant has those dimensions, and is therefore sometimes called Terminology, action has the dimensions of energy×time. This technical term is an historic relic of the 17thĬentury, before energy and momentum were understood. Result, one common format being: (quantity) ± (absolute uncertainty Usually attached to the quoted value of an experimental measurement or Quantity itself it is called an absolute uncertainty. When an uncertainty is expressed in the same units as the Measurement uncertainties that were used in the calculation of that In a result is due to the combined and accumulated effects of these There may be inherent quantum uncertainty due to Heisenberg's uncertainty principle. To inherent variations in the measurement process itself. The uncertainty in a measured quantity is due Has additional cartoon definitions, not included in this document.Īccurate. Use your browser’s search tools to find other words.Ī related document, Jack Holden's Illustrated Dictionary of Physics Input and suggestions for additional troublesome terms, or for clearer statements about these,Īre invited. This document is continually under development and may never be Kirkpatrick & Wheeler, Physics, A World View, Saunders, Glossary for elementary physics may be found in Appendix G-1 of Some words have subtle and intricate meanings that cannot beĮncapsulated in a short definition. It focuses on those terms that give students particular difficulties. This glossary is not intended to be complete. Standard dictionaries are not always the best source of useful and Technical terms of science have very specific meanings. A Glossary of Frequently Misused or Misunderstood Physics Terms and Concepts.īy Donald E.
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