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)

Here, Distance between two cities $=150 \,km$
Resistance of the wire, $R=\left(0.5 \Omega\, km ^{-1}\right)(150 \,km )$
$=75 \,\Omega$
Voltage drop across the wire,
$V=\left(8 V km ^{-1}\right)(150 \,km )=1200\, V$
Power loss in the wire is
$P=\frac{V^{2}}{R}=\frac{(1200 \,V)^{2}}{75\, \Omega} 19200 W=19.2\, K W$