A vacuum flask contains a double-walled glass vessel where the air between the walls has been removed to create a vacuum.
How does this vacuum help to keep the contents of the flask hot?
It reduces thermal energy transfer by radiation.
It prevents thermal energy transfer by conduction and convection.
It prevents thermal energy transfer by conduction only.
It increases the rate of convection within the vacuum space.
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.