Brian M. answered • 01/09/20
Ivy League educated, Silicon Valley experience Math & Engineering
First, let's clarify your question. You state that you think electrical wires are not covered with plastic materials, when in fact they are covered with plastic materials. Given the assumption that you have bare wires, which do not have plastic covering, then how is it possible to avoid a short circuit when it rains?
The key to your answer is to prevent an electrical path from one wire to the other wire. Normally, plastic would do that, but we are assuming here that there is no plastic around. The wires can be wrapped in any non-conducting material (i.e. wood, glass, ceramic, etc.) to prevent any electrical path between the two wires. Care must be taken to prevent water from working it's way around (or seep through) the protective material.
If one were on a deserted island and there was no such non-conducting material available, one could still run ac across the wires by separating the two wires as far as possible apart. Even though each of the wires would/could get wet, as long as there was not a continuous path of water (i.e. river, lake) between the two wires, the ac circuit would work. Air would be used to insulate the two wires in this case. Air does conduct, but very little. It usually requires tens of thousands of volts to make air conduct electricity (as in the case when lightning occurs and the air actually does conduct electricity.
