Four thermal insulation materials are supplied as sheets. The individual sheets of the four materials have different thicknesses. A technician makes one roof panel from each material and tests each panel on the same model room. Every panel covers the same roof area. Each test starts with the room at an internal temperature of 35 °C, and the temperature decrease after 20 minutes is recorded.
Which additional condition is needed for a valid comparison of the materials?
the completed panels have the same total thickness
the completed panels contain the same number of sheets
the materials have the same thermal conductivity
the panels produce the same temperature decrease
104 exam-style questions on AQA GCSE Physics 1.2 Conservation and dissipation of energy, covering 1.2.1 Energy transfers in a system and 1.2.2 Efficiency. Each one has a worked solution and a mark scheme showing where the marks go.