Question

The power loss in 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

Hint: The power loss takes place in cables in the form of heat while transferring the electrical power. Also, the power supplied to the generator can be obtained by the product of voltage across the terminals and current.

Formula Used:
The power loss in the cable can be expressed as: ${P_{{\rm{loss}}}} = {I^2}R$
here, $I$ is the current in the cable and $R$ is the resistance of the cable.

Complete step by step answer:
The very important application of transformers is in the transmission of electrical power from one power station to another, where it is used. During the transmission of electricity, there is one most important concern is power loss in transmission lines in the form of heat, which is dissipated due to the resistance of the conductor.

Let us suppose if $I$ is the current flows in the transmission cable and $R$ is the resistance of the transmission cable, then the power loss in the cable can be expressed as, ${P_{{\rm{loss}}}} = {I^2}R$
The power loss can be decreased by reducing the current and resistance of the transmission cable.

We know that the power transfer by the generator is expressed as $P = VI$, here $V$ is the voltage across its terminals. Since $I = \dfrac{P}{V}$, so for a particular amount of power $P$, the power loss when the value of $I$ or $V$ is high.Thus, the power loss is less in transmission lines, when both voltage and current are more.

option B is correct.

Note:The cons of transmitting the electrical power at low voltage:
1. Huge length of cables has high resistance so high power loss takes place.
2. Large voltage drop occurs along the line.
3. Thick wires have to be used for large current and maintain the resistance wires low.
Thus, power transmission over long distances at low voltage and high current is not efficient and economical.