# Tag Info

## New answers tagged si-units

6

This is a relatively tricky one, because it involves the differences between the $\mathbf B$ field and the $\mathbf H$ field in the SI and CGS systems, and those relationships change in the different systems. In short: Oersteds are used to measure the $\mathbf H$ field in CGS units. Teslas are used to measure the $\mathbf B$ field in SI units. In the SI ...

9

They are technically units for incommensurate quantities, but in practice this is often just a technicality. The magnetic field that makes sense ($B$) is measured in teslas (SI) or gauss (CGS), and the magnetic field that people spoke about 100 years ago ($H$) is measured in amps per meter (SI, also equivalent to a number of other things) or oersteds (CGS). ...

4

From a quick google search, it seems that Oersteds are used for defining magnetic field strength and Teslas are used for defining magnetic field strength in terms of flux density. They seem to not really be meant to be converted between, though you technically can (as evidenced by the other answers here). This website and this website might be helpful to ...

0

Quoting from the Wikipedia page on the CGS system: The e.s.u of charge, also called the franklin or statcoulomb, is the charge such that two equal $q=1\:\mathrm{statC}$ charges at a distance of $1\:\mathrm{cm}$ from each other exert an electrostatic force of $1\:\mathrm{dyn}$ on each other. The e.m.u. of current, also called the biot or abampere, is the ...

0

The ampere is used, among other things, to derive the volt, which is the electric potential difference that a current of one ampere has to flow across in order to deliver a power of one watt. (The watt itself is defined mechanically, from second, meter and kilogram). One volt is around the same order of magnitude as the potential differences commonly ...

4

The kilogram is currently defined, as you well note, as exactly the mass of the International Prototype Kilogram, and by definition the mass of the IPK is $1\:\mathrm{kg}$ with zero error. This definition took over from the previous one (the mass of $1\:\mathrm{dm}^3$ of water at $4°\mathrm C$ and sea-level pressure) because the previous one was hard to ...

1

This definition isn't obsolete, by definition, because we are still using it. There are, however, efforts underway to redefine the kilogram. One proposed definition is based on the watt balance, basically defining the kilogram in terms of the electrical units volt and ampere. Another proposed definition, called the Avogadro Project, is in terms of the mass ...

0

The concept of 'independence' of units is difficult to maintain. For large distances for example, we tend to use light-hours or light-years, effectively merging length and time. As Wrzlprmft already pointed out, you could reduce all units to numbers introducing similar concepts. I tend to treat units as a concept to make things easier – both in everyday ...

3

VA is used for apparent power and reactive power. Watt is used for active power. An inductor or a capacitor in an AC circuit does not dissipate energy, because the current and the voltage are 90° out of phase: energy flows into them during half the cycle, but it flows back during the next half cycle. The power lines have to supply that current however, and ...

-1

You can reference these links: https://en.wikipedia.org/wiki/Volt-ampere https://en.wikipedia.org/wiki/Watt The prefex Kilo simply means 1000. So a Kw is 1000 watts and a KVA is 1000 volt-amperes. Hope this helps!

2

This is a fairly subjective question. I do not think there is a need for such a constant. Why? First, lets look at... The definition of the mole Taken from Wikipedia: ... is defined as the amount of a chemical substance that contains as many elementary entities, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of ...

Top 50 recent answers are included