Dear Bill and All,
You are quite right in what you say here. However have you considered the
added advantage of being able to compare energy sources.
For example, I have gas supplied to my house and this is measured in cubic
metres with an energy content that multiplies to give me my energy purchases
in megajoules. Then my electrical energy account arrives and it informs me
of the amount of electricity that I have purchased in kilowatt-hours. While
I am able to do the necessary calculations to compare the energy content of
these two accounts I suspect that there are not too many others in my street
who could do likewise.
On a more radicle level, have you considered buying petrol in energy units;
instead of 'fill 'er up', you could say 'Could I have 5 megajoules please?'
After all it is the energy that you are buying!
Cheers,
Pat Naughtin
CAMS - Certified Advanced Metrication Specialist
- United States Metric Association
ASM - Accredited Speaking Member
- National Speakers Association of Australia
Member, International Federation for Professional Speakers
--
on 2002/03/03 14.05, Barbara and/or Bill Hooper at [EMAIL PROTECTED]
wrote:
> on 3/2/2002 7:38 PM, Joseph B. Reid at [EMAIL PROTECTED] wrote:
>
>> As for electricity consumption kWh is more comprehensible
>> than J, again because we think of time more in terms of hours than seconds.
>
> I can't agree. Joules measures the amount of energy we've used. There is no
> reason why that has to be considered in relation to how fast we used it (the
> power in watts or kilowatts) or how much time it took for us to use it.
>
> That would be like measuring distance in kilometre-minutes per hour,
> found by multiplying the speed (in kilometrs per hour) by the driving time
> in minutes. It could be done, but when you get an answer (say 825 km-min/h,
> from driving at 55 km/hr for 15 min) how does it relate to how far you've
> gone? (It is13.75 km.) How does 825 km-min/h tell you any more clearly that
> you've gone 13.75 km?
>
> Similarly, 55 kW means you use 55 kJ each second, so if you use energy at
> that rate for 15 minutes (which is 900 s), you find you have used
> 55 000 kJ (or 55 MJ) of energy. That value can be related to the heat energy
> produced (measured in joules) or mechanical energy produced (in joules) or
> potential energy of water pumped uphill (in joules), none of which is easy
> to compare with 13.75 kilowatt-hours. Joules (and of course kilojoules and
> megajoules) are by far the more comprehensible way to measure electrical
> energy.
>
> It is BECAUSE we measure elecrtrical energy in kilowatt-hours that most
> people find te measurement of energy to be incomprehensible. Most people
> don't even know the difference between a kilowatt and a kilowatt-hour
> because they confuse the two.
>
> Regards,
> Bill Hooper
>
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> Do It Easy, Do It Metric!
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>
