3 ms·

They're measuring the same thing. Except a joule is one watt-second, which is an inconveniently small unit when talking about large energy storage like an EV ba

They're measuring the same thing. Except a joule is one watt-second, which is an inconveniently small unit when talking about large energy storage like an EV battery. It would be like road signs measuring distances between cities in inches. Besides, energy has long been accounted for in hour-based units. Your power bill, for example. It's just easier to use those same units when thinking about storage, rather than rebasing everything around seconds.

eru 6y ago
I know that they are both measuring energy. It's just that Watt is usually defined as Joule / second, so Joule seems more fundamental. > They're measuring the same thing. Except a joule is one watt-second, which is an inconveniently small unit when talking about large energy storage like an EV battery. That's what we have SI-prefixes for. A Watt-Hour is also pretty small. We usually use Megawatt-hours or so. Using Giga-Joule instead wouldn't be too much of a difference. > Besides, energy has long been accounted for in hour-based units. Your power bill, for example. It's just easier to use those same units when thinking about storage, rather than rebasing everything around seconds. Yes, tradition seems to be the real reason.
- __s 6y ago
  Unfortunately seconds & minutes & hours aren't metric
  - Reason077 6y ago
    Exactly! There wouldn't be a problem here if there were 1000 seconds in an hour.
  - eru 6y ago
    True scientists use natural units anyway. https://en.wikipedia.org/wiki/Natural_units https://en.wikipedia.org/wiki/Natural_units ;)
- TheOtherHobbes 6y ago
  Electrical goods are labelled with kW ratings, and W is just V * A. (Although not many non-STEM people know that.) kWh makes sense as an intuitive unit because it makes it easy to work out how much your heater costs to run for an hour. You can do the same calc in Joules but it's far less intuitive to convert a rating in J/s into J/hr into $/kJ (or worse $/MJ)
  - eru 6y ago
    Mostly agreed. It's not so much that W : = V * A, it's that V is defined as V := W / A. Or to be more precise and pedantic, V := J / C, Joule per Coulomb. In any case, Volt is the derived unit, and Joule is more fundamental.

eru 6y ago

I know that they are both measuring energy. It's just that Watt is usually defined as Joule / second, so Joule seems more fundamental. > They're measuring the same thing. Except a joule is one watt-second, which is an inconveniently small unit when talking about large energy storage like an EV battery. That's what we have SI-prefixes for. A Watt-Hour is also pretty small. We usually use Megawatt-hours or so. Using Giga-Joule instead wouldn't be too much of a difference. > Besides, energy has long been accounted for in hour-based units. Your power bill, for example. It's just easier to use those same units when thinking about storage, rather than rebasing everything around seconds. Yes, tradition seems to be the real reason.

__s 6y ago
Unfortunately seconds & minutes & hours aren't metric
- Reason077 6y ago
  Exactly! There wouldn't be a problem here if there were 1000 seconds in an hour.
- eru 6y ago
  True scientists use natural units anyway. https://en.wikipedia.org/wiki/Natural_units https://en.wikipedia.org/wiki/Natural_units ;)
TheOtherHobbes 6y ago
Electrical goods are labelled with kW ratings, and W is just V * A. (Although not many non-STEM people know that.) kWh makes sense as an intuitive unit because it makes it easy to work out how much your heater costs to run for an hour. You can do the same calc in Joules but it's far less intuitive to convert a rating in J/s into J/hr into $/kJ (or worse $/MJ)
- eru 6y ago
  Mostly agreed. It's not so much that W : = V * A, it's that V is defined as V := W / A. Or to be more precise and pedantic, V := J / C, Joule per Coulomb. In any case, Volt is the derived unit, and Joule is more fundamental.