In light bulbs, when it says "7 watts" in the label does it mean 7 watts per second or hour?

Question

I just need to know about how much a 7 watt bulb would costs me per hour.

Answer 1

using water in a pipe as an analogy for electricity in a wire, think of it like this:

amps = the volume of water flowing (the current) thus,

amp hours = the volume flowing in one hour

volts = water pressure

ohms = resistance = pipe diameter (small diameter = high resistance)

watts = a measure of the the actual power of the water which is pressure multiplied by volume (in electricity, voltage multiplied by  current)

For a light bulb since the voltage SUPPLY is constant, a 100 watt bulb must use more current than a 60watt bulb because it has a thicker wire which allows more current to pass due to less resistance in the pipe.

Answer 2

Watts have nothing to do with time. The power company charges you for watt-hours. A 7 watt bulb will that's left on for 1-hour will use 7 watt-hours, 2-hours is 14 watt-hours... The national average for 1000 watt-hours is about 10 cents, so a 7 watt bulb that's on for 1 hour would cost .07 cents. You'ld have to leave that bulb on for 14 hours, 17 minutes, and 9 seconds before it would cost you 1 penny.

Answer 3

I do not understand why everyone is making this confusing and hard. The 7 watt light you mention uses 7 watts of power for every hour that it is on.

****** tsatkmax  You need to rethink your answer. It makes no sense!!!

If the bulb used 7 watts of power per second it would use 7 x 60 seconds or 420 watts a minute.

420 watts x 60 minutes(1 hour) would be 25,200 watts an hour.  That would be 25,200 watts and hour x 24 hours in a day or 604,800 watts in a day. That is 604.8 kilowatts of power. I just got an electric bill today I only used 942 kilowatts of power for the whole month and I have a four bedroom home. *******

Answer 4

It's not in time - 7 watts constantly in use.

Answer 5

Wattage is  the amount of power to operate the lamp and not a function of time. You pay for energy on the basis of this value factored with time to make kilowatt hours, The terms are a bit misleading, you dont get any idea of light output (which is measured in lumens) which is rather more important, but I suppose you have to have some basis for comparison (longevity and capital costs might be other comparisons).

Answer 6

It is in hours.

Until I seen some of the other answers, I thought everyone knew that.

Example: if you use the 7 watt fixture, or power consuming item for two hours, it would have used 14 watts.

EDIT: Just seen your added question.

If you run a 7 watt bulb, or any 7 watt item for 143 hours, it'll cost you about 8 cents. That's the cost here.

Answer 7

Neither.  You multiply the (kilo)wattage by the time in hours to get "kilowatt-hours" - kWh, which is what you are billed by.

If you use a 7 watt bulb for 143 hours, you will have used 1 kWh, which will cost you about $0.07 CDN.

Power (watts) = Work (energy in joules) / Time (seconds).

When you multiply watts by seconds, you get energy in joules.

The more energy you use, the more the hydro company bills you for.  It's not how fast you use it, but how much you use.

Answer 8

without going into technical terms, the answer to your question is  seconds.  watts is energy used per second.

pugpaws2 and rangedog are both incorrect, the others answers are all ok