Pardon me, I'm a total newb to electronics. My question is, when a device is measured in watts, such as a 60-watt light bulb, is this ALWAYS supposed to be assumed to be watt-hours, i.e. 60 watts per hour?
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Energy is an amount, while power is a rate at which energy is used.
Watt-hours are like buckets, and watts are like buckets per hour. If you have 5 buckets of energy and you pour one bucket per hour, you'll be able to pour for 5 hours before you run out.
If you turn on a 60-watt light bulb for 1 hour, you have used 60 watt-hours of energy. If you use it for 2 hours, you have used 120 watt-hours of energy. If you turn it on for only 1 minute, you have used 1 watt-hour.
It's a little confusing since the "per hour" is inside the term "watt", so to make the rate into an amount, you need to multiply by a time unit to cancel it out.
It would be a lot more intuitive if we worked in kilojoules and kilojoules per hour. :)
One point not yet mentioned: a 60 watt bulb will use 60 watt-hours per hour, or 60 watt-seconds per second, or 60 watt-microseconds per microsecond, or 60 watt-centuries per century. In other words, the "watts" part of the bulb's power usage has nothing to do with hours or any other unit of time.
Stimpy, the power rating tells you the rate at which the device consumes energy. So yes, a 60-Watt bulb will consume 60W*h or 0.06kWh of electricity in one hour. Watt-hours measure energy consumption. There is a simple little page here that shows some calculations.
The concept of 'Watt-hours' as Watt x Hours will be confusing to someone who cannot conceptualize Watt - being 'enegergy used per amount of time'.
I sometimes try to explain this using more familiar concepts: If we use the term 'Keem' in stead of 'km/hour', one could use 'Keem-Hour' to describe distance travelled - going 60 Keem for half an hour means you've travelled 30km as 60 x 0.5=30
Just like a rental company that's interested in the distance your travelled in their car, the energy company is interested in the energy used - they will charge you per Watt-hour. If a Watt-hour costs 1c, it will cost you 60c if you leave a 60 Watt lamp on for one hour.
You are correct in assuming a 60 watt device will consume 60 watt-hours in one hour, but the former (power) is a rate, the latter is an amount (energy).
protected by clabacchio♦ Dec 4 '13 at 10:48
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