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Question:

Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5Ω. The power loss in the wire is?

19.2 J

12.2 kW

19.2 W

19.2 kW

Solution:

Total voltage drop = 150 × 8 = 1200 V
Total resistance of wire R = 0.5 × 150 = 75 Ω
Power loss = V²/R = (150 × 8)² / (0.5 × 150) = 1200² / 75 = 19200 W = 19.2 kW