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10_Ch 17 College Physics ProblemCH17 Current and Resistance

# 10_Ch 17 College Physics ProblemCH17 Current and Resistance...

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78 CHAPTER 17 17.16 We assume that your hair dryer will use about 400 W of power for 10 minutes each day of the year. The estimate of the total energy used each year is ( ) ( ) ( ) min 1 hr 0.400 kW 10 365 d 24 kWh d 60 min E t  = = =   P ( ) If your cost for electrical energy is approximately ten cents per kilowatt-hour, the cost of using the hair dryer for a year is on the order of \$ 24 kWh 0.10 \$2.4 or ~\$1 kWh cost E rate = × = = 17.17 The resistance is 9.11 V 0.253 36.0 A V R I = = = , so the resistivity of the metal is ( ) ( ) ( ) ( ) 2 2 3 8 4 0.253 2.00 10 m 1.59 10 m 4 50.0 m R d R A L L π π ρ × = = = = × Ω⋅ Thus, the metal is seen to be silver .
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