Telephone and electrical wires "sag" in the summer, in hot weather. This is because the wires, like most materials, expand when they are heated. The additional length means that the wires lose tension and sag or droop. In the winter, the wires become shorter, and they may break if too tightly strung.
When metals (like the copper in the telephone wires) gets exposed to heat, they expand (thermal expansion) and when the get cooled they shrink. This directly implies that cables are longer in summer when it is hot. So telephone wires are longer in the summer.
When they get colder, they will get shorter - and the tension will increase. That might make them break.
so it can survive
Bofore the question can be answered, it needs to be properly rephrased.The question contains a grammar error that is all too frequent these days... non-agreement with the subject in number (singular or plural). We need to be more careful of such simple grammar slip-ups. Poor grammar betrays a lack of education and an imprecision of thought.Correction: Why are telephone wires left slack?This error is creeping into speech today...from even the news anchors... through the contraction of "is" following the word "there", e.g. "there's too many jobs being lost...".Correction: There are too many jobs being lost...
beacuse is good
I'll take that as "How are telephone wires connected?" but it's still unclear what you want to know. Telephone wires are connected just as any other wires are connected. By screw connections, by soldering, by crimping.
so it can survive
When a pole shifts with the earth it will pull the wires apart and cause a break somewhere in the line. The poles are meant to suspend the wires in air, not to stretch them... Accurate answer is the lines will break. While breaking is not normally due to poles shifting, that could happen. The reason the wires are slung loosely is because of the expansion and contraction properties of the metal wires. If you look at the lines in the winter, they do not sag much (are tighter) and in the summer the sag is pronounced (looser). If they were strung tightly, they would eventually break during the cold weather.
If the telephone wires were made tight in the summer and then suddenly exposed to cold temperatures, they could potentially contract. This contraction could cause the wires to break or become damaged due to the sudden change in tension. The wires could also lose some of their flexibility, making them more susceptible to snapping or failing under stress.
Copper is used for telephone wires because it is the second best conductor of electricity after silver (which is a little pricey).
Telephone and electric wires stretch (expand) when the weather is hotter. Conversely, in the winter they shrink. Without some slack, they could become too tight and break, or pull loose from their anchors.
what happens to telephone wires on hot days