Q.

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 0.5 Ω. The power loss in the wire is             [2014]

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

Ans.

(2)

Here, 

Distance between two cities = 150 km

Resistance of the wire, R=(0.5Ωkm-1)(150km)=75Ω

Voltage drop across the wire, V=(8Vkm-1)(150km)=1200V

Power loss in the wire is

P=V2R=(1200V)275Ω=19200W=19.2 kW