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Home Q & A Board Science-Related Homework Help Physics
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smooth15 smooth15
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11 years ago
How much energy does a 100 watt light bulb use in 1 hour?  Express your answer in joules and in kilowatt-hours. Also find how much money it costs if electricity sells for 10 cents per kW-h.
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#1
11 years ago
Energy used is 0.1 Kw-hr or 3.6 x 10^5Joules

It will cost $0.01 per hour to operate.
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#2
11 years ago
(a) By definition, a watt is one joule per second. Since 1 hour = 3600 seconds, we see that:
P = W/t ==> W = Pt = (100 W)(3600 s) = 3.6 x 10^5 J are consumed.

Then, since 100 W = 0.1 kW, we have:
W = Pt = (0.1 kW)(1 hr) = 0.1 kW-hr.

(b) Since electricity sells for $0.10 per kW-hr, it costs $0.01 to run the light bulb for 1 hour.

I hope this helps!
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