On Thursday, 12 September 2019 17:26:28 UTC+1, John Rumm wrote:


I find just being able to think in terms of dimensions - even if not
doing an accurate analysis on paper, it a very useful tool to catch
errors, and would also stop lots of silly mistakes.

Like how many times you see people talk about kW when they mean kWh or
vice versa.

but for what they are talking about it rarely matters to average users.
What does the Kwh mean on fride/freezer consumption.
such as 124Kwh

note that oa.com uses an uppercase K
argos use kWh/year lower case K updercase W



When buying a kettle I found the figure of 3kw more useful than the fridge version and more useful than 10.8 mega joules of energy.

calories is an even more weird one.

a drink I have here per 100ml is 6kJ or 1 Kcal
an average adult 8400 kJ or 2000 kcal

Is that 2000 calories or 2000 kilo calories which is 2 mega calories :-)


Just a basic understanding that the unit of energy is the
Joule, and that power in Watts is a measure of the rate of flow of
energy. Hence 1 Watt equates to one J/sec. Or energy over time. If you
then multiply by time, the two times dimensions cancel out and you are
left with just energy.

I'm left knackered ;-)