# Watts was defined as J/sec

Gold Member
I thought watts was defined as J/sec . So how can something be rated in watts/hour? Doesnt that mean Joules per second per hour???

russ_watters
Mentor
Where are you seeing this? You sure it isn't watt-hours (w * h)? A watt-hour is a joule per second of power - for an hour.

cepheid
Staff Emeritus
Gold Member
I've never heard of anything rated in W/hr. Your electricity meter shows your energy consumption in kWh (kilowatt hours), which would be Jh/s. So clearly one kWh = 3600 J (I hope I did that right). Are you sure the Watts and hours were not being multiplied in the example you saw?

edit: russ was quicker on the draw.

Gold Member
I thought like, your electricity bill is measured in KW/H.... is it suppose to be KW*h?? I dont have it written down anywhere, i just always remembered electricity as being generated as KW/H..... have i just been living with a bad assumption for these past few years lol

Gold Member
lol oh man, so ive been remembering and writing it down incorrectly? lol oh man... im an idiot.

So 1 KWh, the thing your billed for... is 3.6MJ?

cepheid
Staff Emeritus
Gold Member
And it seems I forgot about the "kilo" in my post

Gold Member
Ah beautiful, now my calculations will make more sense.

dextercioby
There's no physical quantity which would have the (SI) units $\frac{\mbox{W}}{\mbox{s}}$.It would be the rate of variation of power (electrical or mechanical) in unit time,but no one asserted a name to it.