Question

The power loss is less in transmission lines, when :

• A. Voltage is less but current is more
• B. Both voltage and current are more
• C. Voltage is more but current is less
• D. Both voltage and current are less

Answer 1

Answer: (C)

Voltage is more but current is less

The power cables have some resistance.

Power lost in the wires can be calculated as $P=I^{2}R$ with $R$ as the resistance of the wires and $I$ as the current that passes through them.
Power at the load is $P=VI$.

From this one can see that if voltage is increased by say $n$ times, then only $\frac{1}{n}$ the current is required to deliver the same power. However, if $\frac{1}{n}$ current is passed on the same wires, only $\frac{1}{n^2}$ of the power will be lost.