Question

Telephone or electric wires are not tightly fixed between two poles. why?

Answer 1

 the wires are made of aluminium which has a property of contracting during winter season. so to avoid breakage of these wires they are fixed loosely between two poles.

Answer 2

Telephone and Electric wires are made of copper and aluminum which have a characteristic property of contracting and expanding. In summer the wires expand and contract in winter. If no gap is left for expansion and contraction the wires will break.So gap  is left between wires.