10_Chapter 17 HomeworkCH17 Current and Resistance

10_Chapter 17 HomeworkCH17 Current and Resistance - 78...

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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 d6 0 m i n Et   =∆= =     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 23 8 4 0.253 2.00 10 m 1.59 10 m 45 0 . 0 m Rd RA LL ππ ρ ⋅Ω × = =×Ω Thus, the metal is seen to be silver . 17.18 With different orientations of the block, three different values of the ratio
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