Question

A 1 km long voltage transmission line has a voltage 400 volts. If the current carrying wire has resistance 0.2 $\Omega$/meterthen how much electrical energy(in joules) will be lost in 0.5 seconds through the whole transmission line?

• A. 400

Answer 1

The correct option is A 400
Energy loss in the electrical transmission line is given by,
$\Delta$$E$ = $I^2$$Rt$.

$I$ is the current through the wire. $R$ is the resistance of the wire. t is the time upto which energy loss is measured.
The voltage on the wire is V = 400 volts. Total resistance of the wire is R = 0.2 $\times$1000 $\Omega$ = 200 $\Omega$
So, current through the line, $I$ = $\frac{V}{R}$ = $\frac{400}{200}$ = 2 A.
Time, t = 0.5 seconds

So, total energy loss in 0.5 seconds, $\Delta$$E$ = $2^2\times 200\times 0.5$ = 400 Joules.