# Tag Info

## New answers tagged si-units

1

The SI units for electromagnetism are based on the ampere, which is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to $2\times10^{-7}$ newton per meter of length. One coulomb ...

1

Coulomb (C) is the derived unit for charge in SI. One coulomb is the amount of charge in one ampere-second. The elementary charge (charge of one proton or (-) electron) is ~1.602E-19 Coulombs. $C = A*s$ The units work out the in the equivalency, which never requires breaking the Coulomb into its base units, as follows: Netwon: amount of force used when ...

-1

The number of atoms or molecules is not dimensionless, it is the way we "count" the matter. Here are some examples to illustrate the fundamental importance of the amount of substance: While $E = m c^2$, you will not extract the same total energy if your fission process is done with 1 atom or with 1 mole of $^{235}U$. Consider the other basic law $PV=nRT$: ...

12

So, here's the thing. The chemistry that underlies molar mass ratios dates back at least to 1805. We've known that if you divide by a certain "relative mass" number you can get whole-number ratios for atoms in a pile of stuff, for that long. It took us about 60 more years to get a handle on how large atoms were with the estimations of Loschmidt, who worked ...

0

Weighing matter isn't the only way to account for how much mass you have, counting the number of fundamental particles g hat comprise it is equally legitimate. Moles , slugs, grams are all units that account for the dimensional quality of mass. Counting moles for that matter is a more precise unit of measure.

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