Why are Watt Hours not Watts per Hour? Are they the same thing?
In: 1289
Watt-hour is watts * hours. This is a unit of energy.
Watts per hour is watts / hours. This is a unit of the rate of the rate of energy consumption.
After converting hours to seconds these units would be equivalent to:
Watt-hours –> Joules
Watts per Hour –> Joules per second per second or Joules / second^2. You might look at this as the acceleration of energy usage.
They are not the same thing.
Watt Hours is power over time.
Using 10 Watts for 5 hours is 50 Watt Hours of energy. 10 Watts for 100 hours is 1,000 Watt Hours.
Either way, it’s 10 Watts of power, but using it longer requires more Watt Hours of energy.
For example, a light bulb is rated in Watts, but a battery is rated in Watt Hours.
A 100 Watt Hour battery could power a 1 W bulb for 100 hours, or 20 W bulb for 5 hours.
Watt-hour is watts * hours. This is a unit of energy.
Watts per hour is watts / hours. This is a unit of the rate of the rate of energy consumption.
After converting hours to seconds these units would be equivalent to:
Watt-hours –> Joules
Watts per Hour –> Joules per second per second or Joules / second^2. You might look at this as the acceleration of energy usage.
They are not the same thing.
Watt Hours is power over time.
Using 10 Watts for 5 hours is 50 Watt Hours of energy. 10 Watts for 100 hours is 1,000 Watt Hours.
Either way, it’s 10 Watts of power, but using it longer requires more Watt Hours of energy.
For example, a light bulb is rated in Watts, but a battery is rated in Watt Hours.
A 100 Watt Hour battery could power a 1 W bulb for 100 hours, or 20 W bulb for 5 hours.
Watt hours is a unit of energy.
A watt per hour /second It is a unit of power that is energy usage per unit of time
and 1 hour =3600 second
1 watthour = 1 joule /second * 3600 second =3600 joule
1 watt-second is the same as 1 joule
1 watt per hour = 1 joule /second / 3600 second =1/3600 joule/second^2
That is a rate of change of power. So 1 watt per hour means the power usage increases 1 watt every hour. So a if a device start to use 40 watts is will use 41 watts after 1 hour, 42 after to, and so on.
You can compare that to the moment. I will use second not hour it just remove constant that is multiple of 3600
The distance traveled will be equal to the energy.
So 1 meter is like 1 joule =1watt-second
The speed will be the power
so 1meter per second is like 1 watt = 1 joule/second.
The acceleration will be like the watt per hour
So 1 meter/second ^2 is like 1watt/second = = 1 joule/second^2
So the watt-hour is the speed and watt/hour is the acceleration. It is quite a different concept.
Watt hours is a unit of energy.
A watt per hour /second It is a unit of power that is energy usage per unit of time
and 1 hour =3600 second
1 watthour = 1 joule /second * 3600 second =3600 joule
1 watt-second is the same as 1 joule
1 watt per hour = 1 joule /second / 3600 second =1/3600 joule/second^2
That is a rate of change of power. So 1 watt per hour means the power usage increases 1 watt every hour. So a if a device start to use 40 watts is will use 41 watts after 1 hour, 42 after to, and so on.
You can compare that to the moment. I will use second not hour it just remove constant that is multiple of 3600
The distance traveled will be equal to the energy.
So 1 meter is like 1 joule =1watt-second
The speed will be the power
so 1meter per second is like 1 watt = 1 joule/second.
The acceleration will be like the watt per hour
So 1 meter/second ^2 is like 1watt/second = = 1 joule/second^2
So the watt-hour is the speed and watt/hour is the acceleration. It is quite a different concept.
Think about a big tank of water.
Now imagine I hook a hose up to it and let water drain out for an hour.
The hose is “a thing that lets water out at a specific rate”. The water that drained is “how much water that hose let out in an hour”.
Watts are like the hose. They’re how much energy gets spent per unit time. But if I asked you “how many hoses per hour does this bigger pipe drain?” that question is weird, because we want “amount of water” not “amount of hoses”.
Same thing with Watts. It says “this much energy moves per unit time”. There’s already a “per time” in it. So if you divide by time again, things get weird.
What makes more sense is “If this pipe drains as fast as 2 hoses, how much water do I get if it is open for 3 hours?” Each hose let out “1 hose-hour” per hour, so this pipe (2 hoses) multiplied by 3 hours drains 6 hose-hours of water in 3 hours. (The answer will be even weirder due to gravity and some other Physics but that’s another story.)
That’s the real trick. The phrase “per hour” means DIVIDE by time. But a Watt-hour is what you get if you MULTIPLY Watts by time.
Think about a big tank of water.
Now imagine I hook a hose up to it and let water drain out for an hour.
The hose is “a thing that lets water out at a specific rate”. The water that drained is “how much water that hose let out in an hour”.
Watts are like the hose. They’re how much energy gets spent per unit time. But if I asked you “how many hoses per hour does this bigger pipe drain?” that question is weird, because we want “amount of water” not “amount of hoses”.
Same thing with Watts. It says “this much energy moves per unit time”. There’s already a “per time” in it. So if you divide by time again, things get weird.
What makes more sense is “If this pipe drains as fast as 2 hoses, how much water do I get if it is open for 3 hours?” Each hose let out “1 hose-hour” per hour, so this pipe (2 hoses) multiplied by 3 hours drains 6 hose-hours of water in 3 hours. (The answer will be even weirder due to gravity and some other Physics but that’s another story.)
That’s the real trick. The phrase “per hour” means DIVIDE by time. But a Watt-hour is what you get if you MULTIPLY Watts by time.
The simple answer is that Watts are already a measurement of rate.
1Watt = 1Joule/ Sec
So a watt-second is a count of energy
Joule/Sec * Sec = just Joules
A watt per second is like a measurement of acceleration – how “fast” is my rate changing?
Watt/Sec = Joules/Sec/Sec.
Using hours is just saying “3600 seconds” in the above math.
Think of it like “mph”, if mph was it’s own unit.
1mph * 1hour = 1 mile.
1mph/1hour = I sped up from 50 mph to 51 mph over the course of an hour.
The simple answer is that Watts are already a measurement of rate.
1Watt = 1Joule/ Sec
So a watt-second is a count of energy
Joule/Sec * Sec = just Joules
A watt per second is like a measurement of acceleration – how “fast” is my rate changing?
Watt/Sec = Joules/Sec/Sec.
Using hours is just saying “3600 seconds” in the above math.
Think of it like “mph”, if mph was it’s own unit.
1mph * 1hour = 1 mile.
1mph/1hour = I sped up from 50 mph to 51 mph over the course of an hour.
Latest Answers