# Light bulb wattage

How may watts does a 60-watt light bulb use in three hours?

60*3=180watts???

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Njorl
Watts are a measure of power. Power is a rate of energy usage. "How many watts used in an hour?", is a nonsensical question.

Sensible questions would be:

-How many kilowatt-hours does a 60 watt bulb use in 3 hours?

-How many joules does a 60 watt bulb use in 3 hours?

Keeping in mind that a watt is 1 joule per second.

Njorl

How many kilowatt-hours does a 60 watt bulb use in 3 hours?

how can i convert that to amps?

Njorl
Originally posted by marshall4
How many kilowatt-hours does a 60 watt bulb use in 3 hours?

how can i convert that to amps?
0.18

You can't.

chroot
Staff Emeritus
Gold Member
60 watts for 3 hours is 60 * 3 = 180 watt-hours. That's the same as 0.180 kilowatt-hours.

Your next question, "how do I convert that [kilowatt-hours] into amps?" is as non-sensical as the first question.

- Warren

FZ+
how can i convert that to amps?
Amps = unit of current = rate of change of charge.

Volts = unit of electric potential

Joules = unit of energy.

Watt = unit of power = rate of change of energy

Kilowatt-Hours = Non-SI unit of energy

You cannot calculate current from power unless you know the voltage, or the resistance.

ya, i'm confused

ShawnD
Watts and amps are both rates. They both stay constant and do not change with time.

To find the amps, divide by the watts by 120.

FZ+
They both stay constant and do not change with time.
Uh... hmm. This is true (as a simplification) in this case, but is not always true.

To find the amps, divide by the watts by 120.
Not neccessarily. Depends on the country.