One kilowatt-hour = 3.6 megajoules. Bill Hooper wrote in USMA 18503:
>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! >+-+-+-+-+-+-+-+-+-+-+-+ Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 TEL. 416-486-6071
