Question

A town situated $20km$ away from a power house at $440V$, requires $600KW$ of electric power at $220V$. The resistance of transmission line carrying power is $0.4\Omega$ per km. The town gets power from the line through a $3000V-220V$ step down transformer at a substation in the town. Which of the following is /are correct

• A. The loss in the form of heat is $640KW$
• B. The loss in the form of heat is $1240KW$
• C. Plant should supply $1340kW$
• D. Plant should supply $640kW$

Answer 1

The correct option is A The loss in the form of heat is $640KW$

Total length of wire = $20\times 2=40km$

Resistance of wire $R=40\times 0.4=16\Omega$ ,

$I_{max}=\frac{P}{V}=\frac{600kW}{3000V}=200A$

Power loss in the form of heat $={I^2}_{rms}\times R={\left(200\right)}^2\times 16=640kW$