15_Chapter 16 HomeworkCH17 Current and Resistance

# 15_Chapter 16 HomeworkCH17 Current and Resistance - Current...

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Current and Resistance 83 (b) The energy used by the oven in 5.0 h is () 3 1 kW 20.0 C s 220 J C 5.0 h 22 kWh 10 J s Et I Vt   =⋅∆= ⋅∆= =     P and the cost of this energy, at a rate of \$0.12 per kilowatt-hour is ( ) 22 kWh \$0.12 kWh \$2.6 cost E rate =⋅ = = 17.33 The maximum power that can be dissipated in the circuit is ( ) ( )( ) 3 max max 120 V 15 A 1.8 10 W VI =∆ = = × P Thus, one can operate at most 18 bulbs rated at 100 W per bulb. 17.34 (a) The power loss in the line is ( ) ( ) 2 2 7 1000 A 0.31 km 160 km 5.0 50 MW loss IR == = P (b) The total power transmitted is ( )( ) 38 700 10 V 7.0 700 MW input = × = × = P Thus, the fraction of the total transmitted power represented by the line losses is
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