Question

in summer electric cables seem to sag , while in winter they seem to become taut again . explain

Answer 1

Having done a lineman course at the start of my apprenticeship, rest assured that the wires are set up to cope with the temperature range they will go through; on hot days, the wire will expand, just as railway lines do (that’s what the gaps were for, and why there are small gaps in metal bridges, covered with a plate). On cold days the wire will contract, but in doing so that increases the tension, and when an accumulation of ice occurs, that can snap wires by overloading them.

In some cases, copper wires had steel wires in the centre to increase the strength, and reduce the chance of breaking. They still lengthen in the heat, and contract in the cold.

Answer 2

Most telephone wires are one or more twisted pairs of copper wire,on which contraction is seen in winter and expansion in Summer.