Question

Give scientific reason.

The telephone wires which sag in summer become straight in winter.

Answer 1

1. Telephone wires are made of copper metal. Due to high temperatures in summers, the metal in the telephone wires undergoes thermal expansion, which makes them expand and look loose. 
2. When the temperature drops in winters, the metal shrinks, which makes the wires stretch and look parallel. This is the result of thermal expansion and contraction of metals.