# kilowatt-hour or megajoule

Discussion in 'Electronic Basics' started by Tim923, Oct 17, 2004.

2. ### Don KellyGuest

No- It is just that historically power is measured in watts and still is.
Hence the use of kWh was adopted for energy. This predated the use of the
"Joule" as a standard energy measure and industry has stuck with it.

In many places the horsepower is not used - kW is used instead. Joules are
used for heat energy but the US still uses Therms. Be thankful you are not
using a stone-furlong -fortnight set of units.

Don Kelly

is valid.

3. ### Rich GriseGuest

I read recently that some city specified wheelchair ramps in centimeters
rise per foot horizontal.

Cheers!
Rich

4. ### John GGuest

I do not know about the US but in Australia car tyres have the rim
diameter in inches and the tread width in millimetres.
This is a multicultural nation!!

5. ### JeffMGuest

some city specified wheelchair ramps in centimeters rise per foot horizontal
We call them tires, but yeah, same here.
How about eye tests? 20/20 vision == 20mm characters readable @ 20 feet.

6. ### William J. BeatyGuest

Is it more direct to measure yards than meters? Or more direct
to measure pounds than kilograms? Answer: no.

Also: (heh) is quantity of electricity measured in coulombs... or joules?

And just how large is a coulomb, in millimeters? About 0.4mm!

For mobile electrons in copper wires, there are around 8.5e22 electrons
per cm^3, and 1.6e-19 coulombs per electron, gives 13600 coulombs per cc,
so each coulomb is about 0.04cm across!

http://amasci.com/miscon/speed.html

7. ### tlbs101Guest

I always wondered why they couldn't have set a Coulomb equal to a Mole
of charge. Either that or create a new electrical unit of charge
equal to a Mole of charge -- how about the Heavi (for Heaviside).

8. ### Rich GriseGuest

Well, no, actually, that means that at 20 feet, you can resolve what
"normal" eyes can resolve at 20 feet. 20/200 means that at 20 feet,
the letters have to be so big for you to resolve them, that they're
the size that normal eyes can resolve from 200 feet, and so on.

At least, that's what they taught me, back when schools actually
taught stuff. ;-)

Cheers!
Rich