a 100-watt light bulb is left on for 14hours. how many joules of energy are used? with electricity at $0.09 per kwh, how much does it cost to leave the light on for 14 h?
2007-01-21 14:01:23 · 3 answers · asked by Christie 1 in Science & Mathematics ➔ Chemistry
100 watt light bulb for 14 hours is 1400 watt hours or 1.4 Kwatt-hrs
at $.09 per kwh, that is .09*1.4= $.126
so, it costs about 13 cents for 14 hours of light at those conditions
1.4 kilowatt hours = 5 040 000 joules (from googles unit converter)
2007-01-21 14:10:19 · answer #1 · answered by enginerd 6 · 1⤊ 0⤋
A watt is one joule per second, there are 3600 seconds per hour. A human produces around 150 W (joules/sec) with moderate exertion, meaning a fit runner might produce that by running eight or nine minute miles, maybe a little faster. Which works out to around 6 mph or thereabouts.
2016-03-29 08:19:18 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Ok, 100 watts *14 hours = 1.4 kilo watt hours (kwh)
1 kilowatt-hour = 3.6×10(6) J , so
1.4 kwh * 3.6 x10(6) J = 5,040,000 Joules
At $0.09 per kwh, 1.4 kwh = $0.126 About 13 cents of electricity.
2007-01-21 14:13:18 · answer #3 · answered by Daremo 3 · 1⤊ 0⤋