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Two wires 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 0.5 Ω. The power loss in the wires is:

1. 19.2 W
2. 19.2 kW
3. 12.2 kW
4. 19.2 J

Correct answer: 19.2 kW

Solution

The total resistance of the wire is R = 0.5 Ω/km × 150 km = 75 Ω. The total voltage drop is V = 8 V/km × 150 km = 1200 V. Power loss is given by P = V²/R = (1200)²/75 = 19.2 kW.

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