Question

Electric wires sag in summer and become taut in the winter. Reason?

• A. They perform oscillations according to changes in the seasons
• B. They expand due to summer heat and contract due to winter cold
• C. They expand due to winter cold and contract due to summer heat
• D. There is no specific reason

Answer 1

The correct option is B They expand due to summer heat and contract due to winter cold

They expand due to summer heat and contract due to winter cold.

Every material expands in heat and contracts in cold. The amount of change depends on the material in question. It is important in construction to take this into account. If the cables were hung too tight in the hot summer, when it got cold in winter they would be unable contract enough and would snap. If they were hung loosely in the winter, then in summer the cables would sag far too much. An engineer must take this into account when selecting the material used and planning how much slack to leave to ensure that they will be reliable in hot and cold conditions.