A 500 W hair dyer is used to dry hair for 6 minutes a day for 3 days. How much energy is used? A laptop uses 75 W. The cot of electricity is 5.6 cents per kWh. How much would it cost to operate the laptop for 24 hours a day for one week? A toaster oven is 85% efficient. It uses 1200 J of energy. How much thermal energy is it producing?
Answers: 1
![500 [W]*[\frac{6min}{1day} ]*[\frac{1day}{24hr} ]*[\frac{1hr}{60min} ]=2.083 [W]](/tpl/images/1008/3164/9da49.png)
![0.075[kW]*5.6[\frac{cents}{kw*h}}]*[\frac{24hr}{1day}]*[1week]*[\frac{7days}{1week} ]=70.56 [cents]](/tpl/images/1008/3164/309ed.png)
![Effic = E_{obtained}/E_{delivered}\\0.85=E_{obtained}/1200\\E_{obtained}=1020[J]](/tpl/images/1008/3164/2ae47.png)
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A 500 W hair dyer is used to dry hair for 6 minutes a day for 3 days. How much energy is used? A lap...
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