Explain the following:
Most telephone wires are made from copper.
(a) The telephone wires break in winter.
(b) Iron rims are heated before they are fixed on the wooden wheels.
(c) The gaps are left between the successive rails on a railway track.
(d) A glass stopper stuck in the neck of a bottle can be removed by pouring hot water on the neck of the bottle.
(e) A cement floor is laid in small pieces with gaps in between.
Sagging of telephone wires during summer is due to thermal expansion.
Telephone wires _________ during winters.
Why are the telephone or telegraph wires laid in summer kept slightly loose, while in winter they are tight?