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 $0.5\, \Omega$. The power loss in the wire is

• A. 19.2 W
• B. 19.2 kW
• C. 19.2 J
• D. 12.2 kW

Answer 1

Answer: (B)

19.2 kW

Answer 2

Here,
Distance between two cities = 150 km
Resistance of the wire, $R = (0.5\, \Omega\, km^{-1})(150\, km)$
$\, \, \, = 75\, \Omega$
Voltage drop across the wire,

\hspace25mm V = (8\, V\, km^{-1})(150\, km) = 1200\, V
Power loss in the wire is
$P=\frac{V^2}{R} = \frac{(1200\, V )^2}{75\, \Omega} 19200\, W=19.2\, KW$