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 +-+-+-+-+-+-+-+-+-+-+-+ Do It Easy, Do It Metric! +-+-+-+-+-+-+-+-+-+-+-+
