Question

The telephone wires break in winter.
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Answer 1

Answer:

Metals expand on heating (in summer) and contract on cooling (in winter). Therefore while putting up the wires between two poles, care is taken that they are kept tight while laying them in winter as they sag in summer due to expansion.

Answer 2

Answer:

Telephone wires break in winters because,

(a) Most telephone wires are made out of copper, which contracts with drop in temperature and hence breaks in winter if it becomes too tight between the poles.

(b) The gaps are left between the successive rails for making space for their expansion when there is rise in temperature in summers.