# natali

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A 100W light bulb is left on for 10hrs. Over this period of time how much energy is used by the bulb?
am i doing this right?

my guess is to convert 100W to kW
and convert 10 hrs to seconds and multiply the 2 together?
which gives 3600J or should i just leave it in watts?

• physics -

A 100W light bulb is left on for 10hrs. Over this period of time how much energy is used by the bulb?
am i doing this right?

my guess is to convert 100W to kW
and convert 10 hrs to seconds and multiply the 2 together?
which gives 3600J or should i just leave it in watts?

• natali -

If you want the answer in Joules (watt-seconds), multiply 100 W by 36,000 seconds.

If you want the answer in kilowatt-hours, multiply 0.1 kw by 10 hours. That's just 1.0 kwh. That would cost you about 15 to 20 cents from most utility companies these days.

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