In power transmission, why is a transformer used to raise voltage on the sending end and lower it on the receiving end?

A transformer is utilized in power transmission systems primarily to stimulate efficient energy transfer over long distances. When voltage is raised at the sending end, the current decreases for the same amount of power transmitted, which minimizes resistive losses that can occur due to the heating of the conductors. By lowering the voltage at the receiving end once the power reaches its destination, the system can deliver electricity at a usable level for consumer applications.

Choosing to raise the voltage helps to reduce the current, and lower current flow translates to a reduction in the power loss, which is primarily dissipated as heat in the transmission lines. As a consequence, this allows for smaller diameter wires to be used, which can offer economic advantages in terms of material costs and structural support requirements. Therefore, the option relating to decreasing the wire size is valid within the context of improving overall system efficiency and reducing infrastructure costs.