Heat expansion

We have seen wires hanging from electric poles. Ever wondered why do they tied the wires between electric poles so loose ? ?????? ????? As I always think myself quite different from others, I just wondered. Another thing is same wires which were hanging loose in winter , look stretched and tightly held between poles in summer ! Why????? This is just an example of heat expansion or thermal expansion . Now what is getting expanded? The wires , obviously . Why do they get expand in summer or when they get heated? It is the property of metals. They get expand when they get heated or exposed to heat. Now the metallic wires between electric poles are not an exemption for this phenomena. As they get expand during summer, if they were tied tightly between the poles , then during summer there is a chance of cutting down of wires because of heat expansion. So in order to prevent that it is better to give extra space to them when they get expand. That's why they are loosely tied. They look sagging during winter and look tightly held up during summer because of heat expansion.