A double-walled vacuum flask is used to keep hot soup warm. The flask has a vacuum in the space between its inner and outer walls.
State the names of the two processes of thermal energy transfer that are prevented by the vacuum.
Explain how the vacuum prevents these two processes.
An electric panel heater is placed on the floor of a cold room. When the heater is switched on, a convection current is formed, and eventually all the air in the room becomes warm.
Explain how the convection current is formed to warm the room. Use your ideas about particles and density.
301 exam-style questions on CIE IGCSE Physics 2.3 Transfer of thermal energy, covering 2.3.1a Thermal conductors and thermal insulators, 2.3.1b Explaining thermal conduction, 2.3.2 Convection, 2.3.3a Thermal radiation, 2.3.3b Surface colour and texture, 2.3.3c Rate of emission and absorption of radiation, and 2.3.4 Consequences of thermal energy transfer. Each one has a worked solution and a mark scheme showing where the marks go.