Telephone lines made of copper wire are installed between poles on a hot summer day. The engineer leaves some slack in the wires, allowing them to sag slightly.
Why are the wires not pulled tightly to make them completely straight?
They will contract on cold winter days.
They will contract on hot summer days.
They will expand on cold winter days.
They will expand on hot summer days.
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.